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Ask Slashdot: Building a Large Email Service 484

Rewd asks: "I'm looking at implementing a large scale email server (cluster) to handle POP3 and IMAP4 for about 25000 people, including a lot of attachments. I'd like to go for an Open Source solution, but a lot of people around here want to go for Microsoft Exchange on NT. Has anyone here successfully built anything like this? Can you recommend any combinations and components which are particularly efficent, capable, secure and reliable?"
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Ask Slashdot: Building a Large Email Service

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  • by Anonymous Coward
    Hmm, Why not use a linux box (just use some good hardware, like UW2-SCSI to start with), and use Q-popper, its used by many ISP's.. works OK for me
  • by Anonymous Coward
    Although they ahve not released the source they are mostly opensouce based. I am shure, given enough horsepower a Linux / FreeBSD solution with perl or php (or C if you are brave) could handle this.

    Will 25,000 user licenses for Exchange not cost the euquivalent of the debt of a small African country - Why not send it on developers to make a (or another as IMP or TWIG may scale that big) free solution in C, Perl or PHP.

  • by Anonymous Coward
    How in the fuck does this piece of repetition get a 3 point rating? It says nothing.
  • by Anonymous Coward
    This will seem somewhat unorthodox, but I would highly recommend taking a look at BlitzMail from Dartmouth College. This solution uses an IMAP-like protocol (but supports POP too) and was originally designed for Mac clients, but its track-record alone makes worth taking a look at.

    Consider this:
    * Very, very efficient. A cluster of six NeXT boxes used to serve 15,000 accounts, and handled more than 200,000 e-mails a day. AFAIK, these machines have now been replaced with 6 Alphas.
    * Unbeatable durability. It was first developed in 1987, and has been in continuous used for more than 10 years! Being a non-commercial product it has not suffered from featuritis or bloat. In other words, it has a very solid code-base.
    * Excellent scaleability. It is designed so that you can simply slot in another machine in the cluster to improve performance.
    * A great feature-set, in particular it has an excellent real-name based user-database as its core, with secure random number authentication.

    And yes, it is free. Source code available etc.

    Take a look at: http://www.dartmouth.edu/pages/softdev/blitz.html

    Skip through the client bits and you will find links to the server software.
  • by Anonymous Coward
    First of all, I would like you to understand a few things that I have ran into when looking at a solution of this size.

    The company I work for has a user base of 19 thousand mail accounts. These run off of Microsoft Exchange on i386 NT boxes. Hold your breath, because getting this `solution' to work demands a cluster of no less than 60 NT machines. All running Exchange in a cluster. At least 10 of them crash each day due to heavy mail load. No, all you NT pundits out there, this has nothing to do with `bad drivers' or `poor configuration'. The amount of mail and their attachments flying around, craves this amount of machines. We have even checked in with Microsoft on this, and they have only told us that getting more redundancy will help this problem. Exchange, from my point of view is _not_ a good solution.

    Then we called Sun. They brought 3 boxes, Sun Ultra Enterprise 450, with qmail and I do believe it was cyrus-imapd. This was because they did not have an `evaluation' of the mail software that was going to power these machines. They did let us borrow the boxes though... Funny i think. Anyway, they set it up during a day, and we let the machines run instead of the Exchange cluster. None of the boxes crashed. They kept going and delivering mail, without _one_ mail going astray for a whole 2 months. Nobody was complaining about mailservers being down or any other kind of cheesy messages in their mail clients.

    Now here is the funny part. The chief of investments called up one day and told us that the sales department from Sun had contacted him to ask him if we wanted to keep the boxes or not. He had told them no, and they were going to pick them up two days after... That meant booting the NT cluster again... After about 30 hours of syncronizing Exchange machines, they were online. Sun came and picked up the machines. My boss said that the chief of investments had the firm belief that Microsoft was The Right Way to Go(TM). Now this decision was _not_ based on our impressions of stability, scalability and reliability. But rather a term of Microsoft buying executives too many lunches...

    So my advise... If you don't want excessive work, stay away from Exchange. Call Sun. They will let you evaluate their boxes. Trust me, they are eagre to sell you their stuff. =)

  • by Anonymous Coward

    I found this while going through the sendmail newsgroup on http://www.deja.com It's about the mail system that earthlink uses. It discusses how they use open source to build a scalable mail system.

    A Highly Scalable Electronic Mail Service Using Open Systems [earthlink.com]

    "...In September of 1997, EarthLink provided email service for over 350,000 subscribers with a 99.9+% service uptime record. In fact, we expect the current system to scale to well over 1,000,000 users without significant alteration of the architecture as presented....."

  • by Anonymous Coward
    My company has over the last 4 months, migrated from a working email system, hosted on (Solaris/Sendmail) & clients (mailtool, Netscape, IE4, generic popmail programs), to Exchange/Outlook.
    The Solaris system is a sparc 10, with a couple of gigabytes. I worked well for years, with little complaint.
    The NT server, with just as much diskspace, has had backup problems, spaces problem (no quota system), is slow at accessing it's 'PST', the single file it stores mail in.
    Additionally, our network calendar system, years in use, was dumped for The Exchange's calendar system. Exchange/Calendar is very limited in memory/diskspace usage, compared to Solaris.
    And of course the NT manager did this on a shoestring, so no backup servers (Solaris does this easily) were bought.

    Now for the best. The company start with Exchange servers at several sites. But has now consolidated to a single server. The other sites must put up with very slow mail access over TI or ISDN connections. Late afternoons many NT systems seem to hang, as the wait on the complex network file access to the Exchange server.

    For my money then nt/exchange system is a waste. It's slow when you need it most, hard to backup, file structure is not easily adapteable to other mail program (like M$ would make a program interoperable).
    Sendmail (on any good U*IX platform) is a bitch to setup, but reliable year after year. Any good pop3 or imap client can be used.
    Go with the Gold, Sendmail!

  • by Anonymous Coward
    Linux IMO is not a server OS, there are some concerns about security, speed and stability. Also the speed at which changes are made can be a problem in a production environment.

    These concerns are, for the most part, unsubstantiated. Recent tests in c't magazine showed that Linux and FreeBSD perform nearly identically well for web serving; FreeBSD is slightly faster serving static content and Linux is slightly faster serving dynamic content. Linux' slow userland NFS is being supplanted by a kernel NFS daemon comparable in performance to FreeBSD's, and Linux is significantly farther along in SMP support than any of the BSDs.

    Arguing about Linux' stability is absurd. Properly administered Linux boxes, like properly administered FreeBSD boxes, can stay up for a year or more at a time. In fact, IIRC, a Linux machine currently holds the uptime record between these two OSes.

    WRT security: well, if one is prepared to admit NT to consideration as a server OS, one certainly cannot write off Linux as insecure. I am not aware of any outstanding security holes in the Linux kernel. Both Linux and FreeBSD are widely deployed commercially, have withstood considerable scrutiny, and are certainly suitable for anything short of mission-critical banking and military use.

    The key theme here is that, in the hands of a competent sysadmin, either Linux or FreeBSD is an excellent choice for a server OS. If the recent influx of Linux newbies has managed to tweak the BSD camp by their exuberance, let me assure you that the recent rise of self-righteous BSD advocacy has been at least equally vexatious to experienced users of Linux and *BSD alike.

    Let me apologize if this has come off as a flame, but it really is time for the Linux and *BSD circles to play nicely and get along with each other. Unsupported statements like "Linux IMO is not a server OS" are flamebait, pure and simple.

  • by Anonymous Coward
    I've done such a thing already with open source
    and it works fine. All users are stored in
    a QI/PH Database which is designed to handle a large amount of mail users and is integrated with sendmail.

    For fetching the mails I mofified popper in a way,
    that it searches for password and mailbox in the
    Database as well.

    All in all it was done within a few days easily.

    Send a mail to 007@freemail.at for further infos if you are interessted in the system.
  • by Anonymous Coward
    When I was working at a large state agency in Texas (rather well run -- Texas goverment is a mixed bag, from third world corruption to world class on the same state office building), I was trying to get a handle on WAN transfer times (Austin, Lubbock, SA, Houston, and so on). I discovered that pulling up Word files with embedded bitmaps was ... interesting. It seems that Word would load the bitmaps (these were signed forms, so they were large and high resolution) in the background as it loaded the document (from Lubbock or wherever, across a T1 to Austin), and, as the user scrolled down the document, LOAD IT AGAIN when the user got to it. Why, I don't know. But that was what was killing the WAN. Word. OK, I called M$ -- I had no real feelings towards them at the time. I did AIX, never worked with DOS and Word (6.0 at the time). M$ was not only completely uncooperative, they looked at the same sniffer logs that I had and claimed that they didn't see the same things. Finally, they called my boss and told him that I was not competent to be working on software as sophisticated as Word. I heard my boss screaming at them from across the floor. I later learned that he had done a lot with OS/2 before Windows95 and disliked M$.

    So no, that isn't a unique story.
  • by Anonymous Coward
    I'm familiar with one setup that used Netscape's messaging systems and they can become a total nightmare. There are lots of wierd quirks about the way it handles aliases, etc, that can be a real giant pain.

    I've never tried any of the open source products on any large scale so I don't know how they perform. I wouldn't go with Exchange if you are looking to do good scalability. It would be nice to run the service on a big beefy box, and Sun boxes are far better than Intels.
  • Unqualified response.

    I saw an NT box running exchange for only about 20 people and the damn thing would keep crashing once a month or so. We moved to Linux / Sendmail / CuciPOP and everything was all good.

    I'm sure FreeBSD would work as well...

  • Sendmail isn't the part that doesn't scale, it's POP3 when dealing with Sendmail files.

  • That has got to be the single most idiotic error message that has ever come out of redmond. That, by far, beats error messages such as "Error 13, your system will reboot now" or anything like that.

    Exchange does suck. Thankfully I've only had to use it once in my life. I'll stick with sendmail and qmail. :)
  • Not server related, but I worked at one site of a very large manufacturer. For MS support they had to sign a support contract and pay for the pleasure, call a 1-900 number and pay again, and only one person was allowed to call it, or pay even more. The combination of having to pay for support, that one guy was usually sick/at "training"/etc, and the typical MS answer, "What, you installed non-MS software on this computer?? We can't help you," made for some interesting conversations with the boss. It was just accepted among the support staff that you delete/reinstall programs or the whole system anytime a problem got too complicated. I just can't understand how that is acceptable behavior for something so basic to your company's computer systems. Yet, every year they get themselves more and more entrenched in MS products and headaches.
  • Are there any web sites with business case studies of implementing open source solutions, be it good or bad? It's important to know when to hold 'em and when to fold 'em with regard to open source things. I've often wondered just how much say Samba, various MTAs, etc can handle. One central resource for this sort of stuff would be quite useful for me a least.
  • You don't need to license NT for 25000 users if all they are using is Exchange. However the licensing costs for Exchange alone will probably bankrupt you.
  • While I am not (thank god) the Exchange Admin, over the 2-3 years we've had it, we've had 2-3 complete mailbox corruption issues and lost the entire database. We've had 3 weeks or so total where it was unavailable (3 1-week blocks).
    It doesn't scale well at all (NT doesn't...so Exchange doesn't) and those boxes look in pain as they try to do what people ask them to. However, response-wise, it frequently "pauses" to check new mail and your composing is also paused...what a great product! :) I am frequently asked by management, why it's so slow.
    Unix solutions will be far less headache if anyone understands Unix in your environment and the support is gonna be worth training someone, versus paying Microsoft to vainly (in our case) strive to repair your dead Exchange databases/servers. Our company is STILL headed into a MS only environment and it's sickening. Ok...enough rant and rave.
  • When I recently had to design a Web-based email service as part of my company's "portal" site, I chose Qmail as the "back end" of the service. I set it up to use a virtual password service (I took one called "vchkpw" and modified it) and set up hashed mail directories to keep the directory structure balanced. I also created a miniature HTTP/CGI server in Perl (it didn't have to be fancy, and it uses the UCSPI-TCP "tcpserver" program for its network front end) and employed some Perl scripts and C programs to allow mailboxes to be created and deleted via an HTTP operation. On our public site, this runs under Solaris; for development purposes, I used Linux.

    On the Web server side, sadly, it's Windows NT and IIS/ASP, with some ASP components including a custom-written client-side mail store. We use the commercial AspHTTP component from ServerObjects to send requests to the mini CGI server on the Unix box when we need to create accounts. We also use AspMail and AspPOP3 to handle sending and receiving messages. (The mail server is firewalled, so you can't connect to it from the outside with POP3.)

    Qmail is definitely industrial strength and free, two qualities that we appreciated. It's also easy to configure and fairly easy to customize. Recommended. Oh, and you can find the end result at www.webb.net [webb.net].


  • How in the fuck does this piece of repetition get a 3 point rating? It says nothing.

    And I suppose yours does?

  • I've recently investigated into switching users from POP to IMAP and have realized that IMAP simply doesn't scale well. Client CPU for doing the type of operations IMAP does is cheap, while server CPU is expensive.

    Cyrus and UW IMAP are not light solutions. They are very large binaries which run from inetd and are anything but clean implementations.

    Really, I'd say stick to POP3 using something like Qpopper or go with a commercial vendor. Qpopper is probably the best POP3 server you are going to find in the OSS world, though it does still run from inetd.

    Open source POP3/IMAP4 servers really are lacking in the Unix world once you get past a certain number of users.

  • The senate uses it for, what, maybe 1000 users (Senators and support)... When they were flooded with email last year, the servers locked up totaly. Many messages for days on end were lost.

    Remember, however, that the version of Exchange the Senate was running was at least two major revisions out of date, running on (I think) NT 3.51.

  • Groupwise? If your company is looking to have the stability of a 'name' behind it, then Groupwise might fit. It works nicely, scales well, is pretty stable, and a whole lot less expensive than Exchange / NT client licenses. ($55 per seat for Exchange solution, less than $20 per seat for Groupwise.) And, you can run it on free server software - Novell run time servers work great for this, since you don't use a Novell file server connection connection for mail. NDS for security and user management, and pretty decent performance on mid-range Intel software, too.

  • Your comments are a little weak, considering the sizes involved. Where's your background on large systems?

    Typical Microsoft tactic - can't stand to have the issues it uses on others applied to its own world.

  • I know for a fact that Lockheed Martin uses Exchange for it's LM-Xpress email program that handles 175,000+ users. How's that for capable? The two important characteristics that they were looking at when selecting an email system were security and reliability (i.e. no lost emails), and Exchange has been a real success.

    Hope you don't mind some questions. How many servers? How much maintenance staff for those servers? How stable is the system? Can you provide more details? We've received lots of details about Exchange systems that have failed, how about providing some more info on a successful system?

    On a related note, anyone who says, "Don't use Exchange because Micro$soft sucks," really needs to be a little more open-minded.

    Agreed. How do you respond to those that say 'Don't use exchange because it crashes all the time, and here's another example'?

  • How about stupidity?

    He was talking about the user interface, not the mail server. The mail server is a hacked Qmail running on Solaris. The web servers executing the mod_perl code are FreeBSD.

    And what does hotmail being owned by Microsoft have anything to do with it? Microsoft bought Hotmail after it had already been established, after all. Unless Microsoft has suddenly added a /cgi-bin directory to IIS, Hotmail is still running FreeBSD and Apache.

    bash-2.03$ telnet www.hotmail.com 80
    Connected to www.hotmail.com.
    Escape character is '^]'.
    HEAD / HTTP/1.0

    HTTP/1.1 302 Found
    Date: Fri, 30 Jul 1999 02:26:01 GMT
    Server: Apache/1.3.6 (Unix) mod_ssl/2.2.8 SSLeay/0.9.0b
    Location: http://lc3.law5.hotmail.passport.com/cgi-bin/login
    Connection: close
    Content-Type: text/html

  • So: Microsoft Sales says that you should use NT because someone who doesn't know what they're doing can successfully configure and maintain it, thus saving on expensive Unix system administrators.

    Then it crashes, and the Microsoft apologists say that it's because it takes an expert to install, configure, and maintain an NT installation, and of course it's going to crash if you have the janitor maintaining it.

    Typical. Just typical.

    My question: If you need a skilled system administrator in the first place, regardless of the operating system, where's the TCO benefit for the Microsoft software?

  • I think it depends upon what you're doing and how you're doing it. POP is straight file slingin', little CPU involved. IMAP is, as you mention, a bit of a hog.

    IMAP for 30,000 users on Linux or *BSD would require a cluster of machines for the front end, but you'd still only need one machine feeding the data into the Netapps on the back end. But the big iron Solaris solution definitely has the cojones to handle this situation without clustering, and will be tremendously easier to configure and maintain than the cluster. And also quite a bit more expensive hardware and software-wise. So it is a tradeoff, and it depends upon how much in-house talent you have. If you have a lot of inhouse talent, the Linux cluster will save quite a bit of money. If you don't, the Solaris solution will require less expensive consultant time to set up and configure, meaning it will be the more cost effective solution. Wanted a simple answer? The only simple answer I can give is "Don't use NT, at least not with Exchange" (grin).

  • OK, here's the scoop:

    Hotmail runs many email servers behind an ip switch (ala F5's BigIP, Ipivot's Broker, Alteon's switch, Cisco's LocalDirector, LinuxDirector, etc). The responses gained from queso or nmap are the answers from the load balancing box, not the mail servers. This has been experimentaly proven and confirmed.

    According to all of their press releases they run sun hardware and solaris.

    Hotmail runs a (heavily) modified Zmailer for inbound connections, and local delivery, probably in some failsafe and distributed manner.

    Hotmail uses qmail for delivery, outbound. This version of qmail is also modified, at least somewhat, and probably a *lot* by now.

  • Here are some ideas that have been used to good effect at other sites, based on anecdotal evidence:

    Qmail - Fast mta, reliable NFS delivery in the Maildir format. Others may vote for PostFix. I don't know it, but it may do as well.

    Netapp - Fast nfs server. Multiple mail server can write to it. There are other NFS solutions from much higher-end storage vendors like MTI and EMC, but that may be more then you want :)

    F5 makes BigIP, a load-balancing ip switch. This lets you multiplex things like pop3, imap, and smtp to a farm of servers, and elimintas the possibility that anyone won't be able to check their mail or won't be able to receive email.

    Cyrus is an imap server. It's pretty good from all I hear. I still have yet to implement it. The other 3 parts I've used a lot, and love 'em.

  • The original poster was an open source advocate. They wanted to be sure that people couldn't say that this was a notes installation or a groupwise installation that the anecdote refers to (though I've heard that these systems have their own issues).

  • SIMS sucks, and is unnecessary and high overhead for this application. I'd chage the recommendation to using veritas filesystem and volume manager w/ a clariion (or other) array, so you get the faster filesystem (essential for mail-queue types of applications - lots of small writes and creates) and allows for live resizing of the filesystem.

    Use cyrus or something else for imap. The above system, according to sun sales literature from about 1.5 years ago regarding SIMS, should support about 250 users. Plus there's no way to recover the SIMS database that I've heard of if there's corruption.

    Good Luck!

  • I highly doubt that every employee at every rent-a-car location has email access or even email access.

  • qmail uses a faster database, called cdb to do fast hashed lookups of forwarding rules. In fact, sendmail modified to use cdb files can drasticly decrease the time it takes to create alias files.

  • Yeah, this is a real filesystem issue you're running into. The time to traverse the linked list that is a directory structures is quite long when you have more then about 1024 files in a directory. The answer in the future is using a different directory structure, and in the short run is to hash things like active mail spools across multiple directories (see qmail's bigtodo patch from Russ Nelson).

    FreeBSD probably would have served you better then linux in this case as well.

    Question: anyone know if future filesystems will address this issue, or is this outside of the filesystem and in the kernel?

  • Performance problems at the outset:

    1) syslog - for this much volume, syslog will slow your system a lot.

    2) Qpopper requires a read through the entire mail file for that user each time mail is checked. For a user with a couple of megabytes of crap (think attachments) this can be a few seconds worth of activity just to get the first 5 lines of each message. Solution? Use the maildir format, which gives each message a file. Don't use MH Mail file format. Why? Because mh will do ungodly amounts of rename() calls each time the user deletes a message from the middle of their mailbox. Maildir is much more efficient.

    3) Sendmail takes a lot of tuning to meet this sort of demand. Sendmail also has a large footprint. Using a mail server like qmail (my pref) or postfix (others' pref) will buy you a lot of performance for a one time learning curve of about a week's time, without having to guess at how to get high-capacity out of the system.

    4) Linux is good, but unfortunately if you're going to do this on a local file system for a system with 25,000 users you need to have a lot of space. I think a Journaled (sp?) filesystem is called for here. Currently for supported tools that really means a commercial unix. I've used solaris and veritas' filesystems a lot, and I know that for a mail queue and for mail delivery veritas does amazing this. In addition, it makes recovery in the case of a system crash amazingly fast, and its snapshot facility allows you options to backup that are better then that is usually available on a mail system (i.e. minimal to no downtime to perform a backup of a stable image of the filesystem).

    Anyway, hopefully I've contributed some useful thoughts to this!

  • by spacey ( 741 )
    I've mentioned this in a couple of other posts here, but since you've directly addressed the shortcoming of the standard unix mailbox format, I have to chime in that qmail's Maildir format addresses the weakness of having to read the whole mail spool, without incurring the overhead of using a remote database (development overhead, mostly, but also a lot of overhead in terms of program size and complexity).

  • Sendmail 8.9, too!
  • It's worth noting that qmail's maildir format is very efficient at handling large numbers of email messages. It also stores the messages in the users home directory which makes the system a bit more secure and easier to track down disk usage. Of course it supports the "standard" unix mailbox format if you want to run with unpatched versions of IMAP/POP tools(why?).
  • One other nice thing about InetMail is that incoming mail is stored in multiple files, so the POP3 server doesn't have to churn through large mailspools when fetching mail.
  • I believe.. But that's still no excuse for the substandard spam-handling of Exchange versions prior to 5.5SP1, you could control which IPs clients can connect from (tcp-wrappers, basically), but that's a layer 3 solution (and a bad one, at that) to a layer 4 problem.

    an MCSE who hasn't used MS products in 15+ months..
  • by greg ( 1058 )
    I've seen some serious Exchange installations. 25000 users is far too much for one exchange machine to handle. I've seen 2000+ users on a quad processor Alhpaserver 4100 with an exchange database over 300GB and growing quickly. You can do 25000 users but you will need many servers each with their own RAID array and some serious, dedicated, professional management. POP3 might be a better option since the server requirements per user are lower.
  • By using some sophisticated tools, [Vendor] experts in Redmond were

    Why obscure the vendors name, when its obvious that the vendor here is Microsoft? Unless there is some other OS and MTA vendor in Redmond Washington...

  • Check out http://andrew2.andrew.cmu.edu/cyrus/ index.html [cmu.edu] for info.

    As for the MTA, well I've seen plenty of votes for Qmail and Exim. I'm still pretty partial to Sendmail though. I think they'll all work (though I've been told Sendmail on a single server probably would have a tough time keeping up with the load on something like this).

    With all of these solutions, if the users are getting much mail, you'll probably have to do something kind of exotic to break up the mail requests across multiple servers. The more transparent you can make this, the better. Either the users will have to know WHICH server thier mail goes on, or you will have to make the multiple servers ALL have access to ALL the mail.

    One possible solution would be to use something like CODA (also from CMU http://www.coda.cs.cmu.edu/ [cmu.edu]). This is a cacheing network file system that you could set up on a backend server (running over something like a multi-ported 100Mbps Ethernet Switch with the multiple client servers on the front-end exposed to the network). When client server "x" gets a request from "joe", "x" accesses the file system and gets all the files in joe's mail box (a series of directories) (the ones requested first, then pre-caching all the others). When joe stops using his files, they are allowed to expire on "x" (releasing the cache for use by mary, or adam). Once downloaded, the files can be manipulated on the client and changes are sent to the server when there is time/bandwidth (I'm not sure how the locking and similar mechanisms work on this ... read the coda docs for details).

    This way, you can dedicate one or more MTA servers to stuffing mail into the backend CODA server, then have one or more client servers pulling the data out and handing it to the clients. You spend most of your money getting a BSB (Big Stinking Box) for the backend, and use cheap, easily-replacable-if-it-crashes machines for the front end.

    Another nice thing about Cyrus: It allows you to set per-user space limitations and access restrictions, and mail sent to multiple users is put into a special cache directory meaning it doesn't take up space for each copy.

    One warning: Cyrus suffers from the same problem as INN's traditional storage system - it eats the hell out of inodes because each message is a file. Most email messages are in the 1-2 K range, so when you create the filesystem for Cyrus, make sure to create the maximum Inodes.

    I know from the docs that CMU uses this on a 10000+ user mail network, and they apparently are quite happy withit. I've heard similar things from other large sites.

    Basically, Cyrus is what Exchange hoped to be :^).


  • Just in case anyone didn't know this, the Cyrus IMAPd fully supports public folders. Scheduling is another matter. For that you need an open source calendaring project. ;-)
  • by X ( 1235 ) <x@xman.org> on Thursday July 29, 1999 @01:09PM (#1776030) Homepage Journal

    The Cyrus server at CMU is probably your best bet. You'll find it at at this link [cmu.edu].

    It's worth noting that this project is currently supporting all of CMU's e-mail needs. It's also my understanding that it forms the basis for Netscape's Message Server and Post.Office. This should satisfy any concerns about it's scalability. It has lots of handy features like kerberos authentication, a database style message repository, support for ACAP, etc.

    Alternatively try QMail [qmail.org]. Personally, while I think it provides better SMTP performance than Sendmail, I'd rather use the Cyrus IMAP server than the UW one (the only one supported by QMail). You could go with using a combo of sendmail|postfix + Cyrus for incomming mail (i.e. what your MX records point to) and QMail for outgoing mail. It depends on your performance needs

    Exchange Server is NOTORIOUS for being both difficult and expensive when you need it to scale to a large number of users, although I understand it's improved substancially since the 4.x days when it was just impossible.

  • I concur....

    for 25k users, I'd go with a higher-class system to support the load that they'd generate.

    I'd recommend running Sun SPARC-based systems running Solaris 2.7 and InterMail, with a fiber-channel storage solution like a A5000. The multi-threaded design of both Solaris and InterMail will do you much better than any Linux/*BSD solution.
  • To put greg's comment into perspective, we have 1200 users on site here, and we have 3 Exchange servers. 2 servers couldn't handle it. Each server is a Compaq Presario (2xP6 @ 350MHz, I think), with 512Mb RAM and several GB HD space.

    I'd seriously look at all other solutions, wether commercial or OpenSource.
  • Sorry man, throwing more CPUs at the problem of mail is not the solution. What you need to do is get a very fast SCSI/raid controller and some high-RPM low-latency/seek time LVD drives or something. Large CPU won't help, since mail is mostly a matter of throwing files from disk to disk over the network. I mean, this isn't heavy rendering or anything.

    So get a good, fast disk subsystem and attach it to whatever Unixoid OS you like. Run Qmail if you like (it's a bitch to configure, and not as versatile as sendmail, and it's not open source but it's fast), or get a bunch of good sendmail admins.

    You can configure any mailer to handle large load on the SMTP side of things by using multiple MX records and mail relays. POP and IMAP are a little tougher.
    I noticed
  • Are you serious? Exchange at this level of usage would be absolutely nuts, but Notes? Puh-leeze.

    Nobody buys Domino for the mail capability, they buy it for the groupware and application system, and they *accept* the mail function that comes with it. The client UI is so amazingly bad that a UI design site did an in-depth critique, attacking pretty much the entire app. (http://www.iarchitect.com/lotus.htm)

    The server is difficult to administer; the user directory is flat, slow and scales badly; and a given user's mail store only *looks* hierarchical, but is actually just one big lump of data which must be read in its entirety, first-in-first-out, for many applications, especially connectivity with third-party apps attempting to access the VIM subsystem (which is itself pretty awful) for messaging. This means that anything attempting to read a Notes message will read every single thing in the mailfile in order of its creation until it finds what it is looking for, including any archived, sent, and deleted items.

    The client is difficult to navigate, crash-prone, and really beats the hell out of a network.

    Hopefully the newer versions are not so bad as 4.1, but I was involved in a rollout of Notes to a mere 600 users at a chemical plant two years ago. Notes was hosted on a single high end NT/Intel box, which should be sufficient for the intended usage. Users were sent to training classes on Notes in small groups twice a day, and their machines were converted to the new mail system while they were in the class. So we knew how many users would be on the system on any given day throughout the rollout. The guy onsite from Bay Networks and I made a bet on when the network would crash from the load - I was within an *hour*. We didn't even get halfway through the deployment before the net died. Not the server, the network. Admittedly, the network was sufficiently stressed and just plain odd at the best of times, which is why the Bay guy had a desk, but 300 casual mail users should not kill a production network.

    (One of the plant managers was upset by the burning fuse I drew up on a whiteboard in the MIS room and updated daily. After I was proven to be exactly correct in my forecast, he bought us lunch.)

    Domino is not a mail system. If you don't need all of the other whiz-bang features of Notes/Domino, don't do it. For groupware it kicks some serious ass, really doesn't have any serious competition, but for straight mail you are better off with nearly anything else. Except Exchange.

    who dumped Notes 5 testing on someone else just this morning, and is still smiling
  • Certainly with Qmail, probably with other MTAs, you need to think about filesystems. mbox mailboxes should NEVER be on an NFS mount, they're bonud to get corrupted (dodgy locking). Qmail's maildir format works fine over NFS, but not all clients like it (no matter if you use a pop server).

    ext2fs returns from write calls while the metadata may still be in RAM cache (making it fast) -- if you want complete end-to-end reliability, that won't do. XFS will fix this for Linux, (as does a tiny patch Linus sent to the qmail mailing list) otherwise FreeBSD may be a better free UNIX to use.
  • I've been with Slashdot for a while (back when it was just a little announcments page on Rob's server, along with his homepage), and I have to disagree that Slashdot's getting worse.

    We have problems, true. But we're getting better overall.

    Anyhow, about Exchange: ouch. The worst part is that in order to use Exchange at work I _have_ to use Outlook. That alone makes it inconceivable to actually WANT to use Exchange. A real turnoff. Outlook 97 was a real bastard; 98 is passable.

    I've got many Unix accounts, and I've had many others, and never lost past email. I only have one Exchange email address, and already I lost 30 megs.

  • I've had good luck using the Cyrus IMAP server and the Exim mail transfer agent (MTA). The Cyrus server handles POP3 and IMAP, and stores the mail in an internal file per message format, and is designed for hosting mailboxes for those without accounts on the system. I've found both Exim and Cyrus to be fast, secure, scalable, and stable for thousands of customers, and I don't see any trouble scaling it further.

  • the solution we use (for +150k users) is to have users divided up and we have a mapping server that does nothing but map user to servers. we have eight sun E5k's that handle the users and two of them run (cough...) Notes. The others run sendmail.
    A couple of them feed into the mainframe systems.
    The only ones that ever give us problems are the notes servers.
    overall it works very well.
  • Have any of you ever administered the pgpkeyserver that works on some servers on the internet?
    Ok, me neither, but the server I work at has a pgpkeyserver, run by our admins.
    We HAD to change to qmail, because sendmail wasn't able to cooperate with the thousands of emails we have to handle in about half an hour (about 7200, which is about 4 incoming mails per second, this being a low number) when the pgpservers synchronized.

    Little side note: we run a 2.0.36 linux kernel, on a single 233mhz intel pentium 2 with 128Mb of ram, and sometime we reach loads of 24 or more when the pgpservers synchronize.

    It is one public key per mail.

    Bulk email, open source, qmail rulez.

  • Ya, cyrus works wonderfully @ CMU...now if someone would only get sieve working .

  • Setup at the old ISP was this

    3 ultra 2's
    512MB RAM each
    30GB array by artecon that was NFS mounted.

    This was slightly overkill for us. A few this to keep in mind.

    1. Have more then on machine running this. I would say use 4 PII's. Use dns round robin for load balancing. If you have the money get a real load balancer. With an NFS disk array and sendmail file locking this isn't hard to administer.

    2. Use as much RAM as you can afford. 512MB min. 1GB to 2GB is better.

    3. Fast local disks. QPop servers files locally. Have at least 4 gig for mail to be queued. We had at least one user trying to cycle 2 gig attachments through our machines every month, Bastards.

    4. Set up qpop (or whatever) in server mode. This will decrease the traffic from you to your raid array. Server mode tels it that it is transfering data across the network, if nothing in the data changes just revert and don't move the extrea traffic.

    5. Disk. We were fine with 30, but upgraded to 50GB with the last upgrade. Artecon NFS mounted to the 3 machines. Look at Netapps though. You can cluster them in a failover config. I have heard of some hardware problems with them though. We pushed 16MB/sec across a peak so make sure you are AT LEAST ultra wide if not ultra2. You could set up a server with the disk attached and let it do your NFS instead of a full network disk thingy.

    6. I'd suggest sendmail, but qmail is nice, too. Sendmail seems easier to set up to use with pine if you want to hook a shell machine up to it with Pine or use a webmail package, but honestly I haven't played with Qmail much.

  • we user

    /var/mail/u/s/user for ours with an Oracle backend for authentication. We tried switching back to /etc/passwd for mail delivery only which immediately shot load up to 12.

  • It's not an open source solution, but you might be interested in Inet.Mail or Inet.Mail Pro from Hethmon Brothers ( http://www.hethmon.com/ ). It runs on OS/2 Warp. The Pro version supports multiple virtual domains, so you probably don't need that. The cost for unlimited users is $200.

    It's heavily multithreaded, so the performance is excellent. I couldn't say whether it's ever been used with 25,000 users, though.
    Timur Tabi
    Remove "nospam_" from email address

  • We use exchange for about 500 users, and it works pretty well for us, but I won't claim to be estatic. We felt that we needed 2 DEC Alpha boxes (dual cpu, 533MHz) to make it happen, and we're using big-time RAID: DEC HZ70 dual controllers.

    Problems: If you don't buy the enterprise version, you have a limit of (I think it was) 17Gig TOTAL of mail... Which came out to about 40 users on our system until we started bitching at people to delete old mail. It really bites because exchange shuts down with no warning when you hit the limit. If you must use exchange, get the enterprise edition, which has no database size limit.

    Exchange's database under 5.0 is guaranteed to corrupt eventually. You need to shut down regularly (at least once a month) and do an ISINTEG, or you get fun things like the President's email being delivered to the Janitor with a header from the Lawyer. 5.5 is a lot more stable, but I still don't trust it enough to not want to run ISINTEG once in a while. To date though, 5.5 has yet to corrupt.

    Make backups!

    Consider a massive farm of smaller Exchanges rather than one large box, and reserve one day a month of downtime for maintenance BEFORE deploying users.

    If you go for a unix box, I'll give you my metric. While working at an ISP, we had a limited budget due to accounting problems (ie: no accountant, so we didn't know how much cash we had. *SIGH*), and we had a unix box in desparate need of upgrading, but it still ran:

    486DX2 66MHz

    narrow SCSI-1 drives

    FULL news feed

    400 domains

    2000 mailboxes locally

    routing mail for another 2000

    web server

    shell accounts

    anonymous FTP

    96 modems doing SLIP, and PPP at 28.8



    and to add insult to injury, it was SCO!

    I wouldn't ask that much out of ANY single machine if I had the choice, and it was SUCH a relief when we got 4 Alphas running OSF/1 (and some telebits) to replace the tired SCO, but you know it can be done with a solid OS. So a 486 properly configured with fast disk and lots of RAM should be able to handle 2 to 4 thousand users. Use of Cyrus or similar types of software will drag that number up, otherwise large mailboxes drag that number down (LARGE POP3 mailboxes on IO bound machines can actually take too long to scan. If POP3 doesn't report the number of messages fast enough, POP3 clients will time out).

    Today, if I were you, I'd get a Sun Netra T1, and add a FibreChannel RAID card, with as much ram as you can cram in (on the motherboard AND the RAID card). That should handle your 25k users on one box in a pinch, but use two at least. Spreading the people out makes everyone breathe easier.

  • I setup and managed a mail system with over 50k users for the state of Oklahoma.

    We used Control Data's MailHub. A system built on a portable x500 database send/pop mail and Perl scripts. It ran on a SUN spark box.

    These days you could replace the hold thing with an LDAP server and Linux.

    I'd use large Intel box (dual PentumIII) with 128m of memory and 19gig of hard disk, mirrored. This would be a good start. Strip down the Linux system, only run mail on it. Put the LDAP on another box same size and power.

    I'd use Open LDAP for the user server. Then write some Perl scripts (Web forms) to update and manage the LDAP data. (The PHP module for Apache would work good too.)

    If needed, use a round robin DNS to balance the load between several POP servers. These servers will all need to connect up to one large file server. I'm using IBM's AFS file system. It's better then NFS.

  • I setup and managed a mail system with over 50k users for the state of Oklahoma.

    We used Control Data's MailHub. A system built on a portable x500 database send/pop mail and Perl scripts. It ran on a SUN spark box.

    These days you could replace the hold thing with an LDAP server and Linux.

    I'd use large Intel box (dual PentumIII) with 128m of memory and 19gig of hard disk, mirrored. This would be a good start. Strip down the Linux system, only run mail on it. Put the LDAP on another box same size and power.

    I'd use Open LDAP for the user server. Then write some Perl scripts (Web forms) to update and manage the LDAP data. (The PHP module for Apache would work good too.)

    If needed, use a round robin DNS to balance the load between several POP servers. These servers will all need to connect up to one large file server. I'm using IBM's AFS file system. It's better then NFS.

  • qmail is actually not Open Source.

    From http://pobox.com/~djb/qmail/dist.html [pobox.com]
    "If you want to distribute modified versions of
    qmail (including ports, no matter how minor the
    changes are) you'll have to get my approval."

    Please reply in email if you feel the need, I'd
    rather not start a flamewar here :)
    Kevin Doherty
  • Acourding to Microsoft, Hotmail _is_ run on top of Solaris. Check out http://www.microsoft.com/ntserver/web/news/msnw/Ho tmail.asp

    They also state that along with Solaris being used, Windows NT is also used, but they fail to mention how/where it is used, so my guess would be as devel, and not production.

    My favorite quote from the article is "Solaris is Hotmail's legacy production operating system". bwuahahaha.
  • by xeno ( 2667 ) on Thursday July 29, 1999 @02:33PM (#1776052)
    I say with relative authority: Puh-leez!

    MS would like people to believe that Exchange is an enterprise-level communications tool, when it fact it is a buchered and bloated decendant of a mediocre 1992 X.400 email system from Data Connection Limited (check out http://www.datcon.co.uk/press/messserv.h tm [datcon.co.uk]) Don't believe the version number; Exchange is in its second major release (4.x really is 1.x, 5.x = 2.x, etc) and still has significant stability problems. [slashdot.org]

    In my experience, Exchange can support 300 users per server happily on commonly acceptable x86 corporate server hardware (say, a 2 processor PII with 512mb ram). It seems that (in my limited experience, lest MS lawyers take this to be a declaration of fact, which it is not) once you've reached this level, doubling the ram and adding more cpu's has only a minimal effect, which means that you really have to add more servers to add capacity.

    Let's do the math. 25,000 users at 500 users per server (to be quite generous) means that you're going to need a Windows NT server farm of about 50 systems just to do email. Again, being generous bargain hunters, let's say you can buy one of these servers for $10kUS. That means you're out $500,000 just for hardware. In my experience, you can support 500 POP users easily on a SPARC 2 or IPX, which can be had these days for about $500 decked out (including a 17" monitor). You could support the same (probably many more) on a $500 x86 box running any of the free *nixes. Assume you blow $500 on disk storage for these boxen just to level the starting line, bringing the total cost to $1000 per. That's still only $50,000.

    One less zero usually gets the accountants' attention on an expenditure like this.

    But let's talk about administrative support. IMHO you're going to need 1:1 admin per NT server at that usage level, given that remote admin of NT is difficult, and 500 users per server is going to prompt more than the occasional pretty blue interface. (Nevermind the security team you're going to need for a major NT installation.) Say a cheap NT admin costs $50kUS including benefits & overhead. You're looking at an HR budget of $2,500,000us. On the other hand, say you splurge and spend $150kUS per *nix admin. If they couldn't handle 10 little boxen apiece, I'll eat the electrons this was posted with. That's an HR budget of $750,000us.

    That's 1/10th the hardware expense and 1/3 the maintenance expense of using Exchange. And that's (a) making some wild assumptions that benefit the Exchange argument, and (b) assumes that you're running *nix on shit hardware. Spend 5 times as much on hardware for new, supported stuff (say $250,000us, which would buy you a couple of well-outfitted Sparc 4500s, or 10 really gorgeous systems from VA Research [varesearch.com]). Your downtime will become next to nothing, you'll still have spent only half of what you would have for NT and Exchange, and your ongoing yearly administrative cost will be 1/3 of the other option. The *nix administrative savings alone will pay for the *nix hardware in a few months.

    Oh yeah. I forgot the expense of 50 copies of Windows NT, 50 copies of Exchange Server, and 25,000 client licenses... (*erk*!!)

  • by tgd ( 2822 )
    Cyrus is probably the way to go. CMU uses it, and it seems to handle their needs. I've used it at three different companies, and particularly liked the fact that it doesn't rely at all on system users, except for password authentication. Its trivial to patch the system to authenticate passwords against a DBM file or MySQL.

    Its also trivial to write scripts to automate the management of the server, so you can create a new user quickly and easily.

    Two years ago I installed Cyrus at a company that was using NT domain servers for their logins on all the client machines. Quick patch to Cyrus to work with PAM, and a SMB PAM module, and people were able to check their mail using their NT passwords without having any security issues of having all those users on the mail server.

    I also hacked something together that automagically created the mailbox when an IMAP connection was attempted with a username/password on the NT domain that a mailbox didn't already exist for, so the NT-centric admins didn't need to ever touch the mailserver.

    The number of users are much smaller, but other installations have shown that Cyrus will scale, so the ability to extend it like this is also important.
  • by linuxci ( 3530 ) on Thursday July 29, 1999 @01:05PM (#1776062)
    At the UKUUG Linux '99 [ukuug.org] conference there was a presentation explaining how they implemented a large scalable mail server using open source software. It was also explained how the total cost of ownership would be much higher if they used an NT solution (even using the figures supplied by MS they'd need more machines and more administrators to keep the servers runnig).

    The open source solution was much more cost effective and has proved fairly stable.

    Unfortunately the proceedings from the event are not yet online, however I'll try and forward you a copy (or post a link to this thread) as it may prove useful to you.
  • by K-Man ( 4117 ) on Thursday July 29, 1999 @01:57PM (#1776066)
    I'm short on time, but I wish to submit what may be the ultimate Exchange story:

    A sysadmin at, ahem, a "large jeans manufacturer" was put in charge of Exchange on hundreds of NT servers. He dutifully logged and reported dozens of bugs, system outages, etc., to MS support, as the thing crashed and burned like the Hindenburg II. After a few months of this, Microsoft decided to act on the problems. The solution was simple: they sent a letter to his boss saying he was a troublemaker.
  • I hear some people near me talking about Exchange [shudder... been through 2 migrations at companies before].

    Knowing MS Exchange is a "Bad Thing", and I'd like to save the company money where possible, I decided to search the web for a collection of "horror stories and MS Exchange"... to my surprise I couldn't find ANYTHING!

    Now I've seen articles here and there (InfoWorld, news.com etc.) about Exchange bugs, but I would have thought SOMEONE had collected URL's and posted them. Nothing. I'd have to do a lot of research to get this info, and given my workload it would be an unwise distraction.

    The second thing I'd like to know, is how much does MS Exchange COST? I know the price varies, and larger companies get breaks if they "cozy" up to MS, but that doesn't help me much. Say a company has 50-150 employees... what does that translate into just for the software licensing?

  • by Steve Stock ( 5156 ) on Thursday July 29, 1999 @02:10PM (#1776074)
    If you are going to setup 25,000 users, do not, repeat NOT, use Exchange.

    Listen to this advice, it's obviously born on the hard back of experience, just as much as me reiterating this same line: do not use exchange.
    For example:

    • Exchange uses a single database (in general) to hold all the mail for a server, the database integrity tools check (and repair) at 1 gig per hour. Now you put 2000 people on a box at say 10megs each, that's 20 hours of downtime to repair (or even check) the mail store. If you do use exchange, have really good backups, it's faster to restore and lose mail than to check the current database.
    • Database corruption seems inevitable, I haven't seen an active high use exhange server that didn't eventually corrupt its database.
    • Exchange is a hardware pig, my experience comes from using exchange on quad PII-400 machines with 0.5gig of ram and we were nearly cpu bound with 3000 users on a box

    This is only a start, but I'm sure other people have many of their own reasons as well...

    I remember our migration of a mere 750 (users) with extreme horror. We had to manually create each user.

    You can create mailboxes in exchange via a config file with the mailbox import tool, although I figured it out by looking at files it created and not via any documentation. With exchange 5.5 I'm pretty sure you can create mailboxes with ldap (although this is far from documented last I looked).

    As to solutions, I haven't used any open source email solutions with more than ~5000 users, for which sendmail and the UW pop3d and imapd worked well for the users that I had (many were very light on email). I'd be really neat to integrate an MTA and an IMAP server with ldap to support IMAP referrals and smart mail redirection. I know some of this is done as sendmail has LDAP patches and example rules for this, but I'm not so sure about IMAP side.

  • by atporter ( 5395 ) on Thursday July 29, 1999 @03:55PM (#1776076) Homepage
    Rule number 1 in Linux -- If it's worth doing, someone probably already has. Earthlink has published a really great paper on this subject. Definately worth the read http://www.earthlink.com/about/ papers/mailarch.html [earthlink.com]
  • We have a cluster of Exchange servers for our ~4000 workers here, and even Microsoft can't get it to work properly. There's a crew of Microsoft folks here, almost all the time, and our staff of full time admins. Just for Exchange. This is an "upgrade" from the single sendmail/imap server that handled the load of the entire company with very little problems. The main problem with Exchange is it's terrible performace, and the way it makes Outlook (or Outrage as we like to call it) hang while doing such complex operations as reading the next message in your inbox. On the bad days, it takes me as much as 5 minutes to switch messages. On the best days it's just irratic. This doesn't even bring up the problems with the feature set. For example, you can't check your mail from 'nix any more, sorry. Frankly, I can't see reason one to use Exchange. Even if you have to run on NT, you do have other options.
  • by ts4z ( 5791 ) on Thursday July 29, 1999 @12:58PM (#1776083) Homepage
    I've never heard about anyone really happy with Exchange. Except maybe Microsoft, but I'm pretty sure they drug the water.

    Check out Cyrus, from Carnegie Mellon, which is gratis (but not free).

    Or maybe you'd like to spend some money. Then there are lots of companies, like Mirapoint [mirapoint.com], who I work for.

  • I designed and currently maintain a FreeBSD system with ~40,000 users, with probably 20-30,000 "active". I only support POP3 access presently, but I'm looking into IMAP. I'm using 2 PentiumII 300s running FreeBSD. One acts as the SMTP deliver-er for all off-site activity, the other the primary POP3 server. Both have 512M of RAM. The POP3 server has 14 4.5G cheetah drives, 2 internal for the OS, etc. and the other 12 inside CMD ultra-daytona external cacheing SCSI-SCSI RAID arrays (RAID-5), each on their own SCSI channel (2 3940UWs in each machine).

    I use the qpopper with a *lot* of local modifications for security and performance. A custom perl+mysql system manages the userids locally and talks to a campus-wide "meta-directory" which allows people to manage the users from their Winblows machines...User management is probably a bigger problem than performance.

    IO will be your biggest concern, followed closely by getpw* calls, network bandwith, then RAM and/or CPU. There are lots of other issues such as expiring mail, preventing/detecting mailbox corruption.

    Cyrus IMAPd will solve a lot of problems with IO bandwidth, quotas, expiring mail, etc...but it will require more RAM to sustain more simultaneous connections, and more disk space as users can/will/should leave more mail on the server. I have not tested Cyrus in a large scale environment...yet...

    Sendmail works well, other mailers such a qmail, etc. may work as well, many claim to be more efficient, but a properly configured sendmail environment is hard to beat...but any reasonable mailer should be adequate, the actual MTA load shouldn't be that great, no delivering to the mailbox, that's another story.

    Feel free to contact me directly if you desire any more details or statistics.
  • That's amazing... we've got 18,000 users using qpopper on a P2-233 ... and no sweat.

    Amazing how little hardware we had to use.

  • I run a large (>>25000) free email service. We started out with qpopper, but quickly had to switch because qpopper does (or at least did at the time) very poorly with large mailboxes. If the mailbox was very large, qpopper would crash leaving the mailbox twice as big as it was before.

    We were using sendmail at the time, so we started using qmail as the local delivery agent. And pop agent of course. Eventually we switched entirely to qmail.

    One thing to watch out for regardless which solution you use is that (last time I looked) linux (or is it ext2?) is limited to 16-bit uids. There's ways to get around that; I just wish we'd considered it when we started.
  • by Outland Traveller ( 12138 ) on Thursday July 29, 1999 @01:18PM (#1776116)
    When you have that many users you have to have a nice structure for the usernames, which isn't the /etc/passwd file. And, you need a mailbox format that isn't linear, like the normal mbox. The rest of the problems can usually be solved with hardware (think about using a raid).

    I know of three potential semi-free solutions.

    Carnegie Mellon Cyrus (go to the FTP site and download the latest version. Don't rely on the way out of date web page to link to it.) IMAP server.

    University of Washington's imapd. This seems to be under more active development, and supports a nice range of features, mailbox formats, and security mechanisms. However, it uses the passwd file (although you might be able to get around this using PAM) and it doesn't natively support quotas. (although you can do this at the OS level.

    Darthmouth's Blitzmail Server: This has been ported to linux, and is *wonderfully* scalable across multiple machines. It inlcudes its own directory services too. The only problem is that it doesn't support Imap (although some work has started on that front), and the only database it supports as a backend is oracle. I would love it if someone hacked it to use mysql of postgresql with IMAP support, but that's a tall order. The client is also under-featured.

    All of these have their drawbacks though. You might wish to go with a commercial IMAP/POP server on linux. There are a few good ones that exist. You definitely don't want to go with exchange. A lot of people go that route because they are forced to. My experience with exchange 5.5 was so bad that I would not recommend it to anyone.

  • I believe Hotmail use Qmail, which is open-source. When MS bought them out they tried to switch to NT/Exchange, but couldn't get it to work, so they're back on Solaris/Qmail now. I believe they support a large userbase which not only have attachements, but a whole lotta spam, to...
  • Horms is the mail dude for ZipWorld, one of the
    larger Asutralian ISPs. They run Linux internally
    and he presented a paper at CALU on building a
    large and scalable mail system.

    http://www.linux.org.au/projects/calu/cdrom/pape rs/horms/

    for the conference paper.
  • by kend ( 22868 ) on Thursday July 29, 1999 @01:09PM (#1776166)
    Sendmail's the answer for us. The only thing that hasn't scaled well is plaintext aliases files: we've got some 20K mail lists, and it's beginning to get somewhat messy, so we're having to go to the non-plaintext solution. But for all the rest, it's stock sendmail with various GUI backends for end-user ease-of-use (and security). Note that we don't have 25K users, but 17K isn't that far off, and we do a *lot* of e-mail.
  • "[Vendor] experts in Redmond..."

    Hmmmm....who could this be?
    Put Hemos through English 101!
  • by FascDot Killed My Pr ( 24021 ) on Thursday July 29, 1999 @01:05PM (#1776172)
    ...except an anti-recommendation.

    If you are going to setup 25,000 users, do not, repeat NOT, use Exchange. I remember our migration of a mere 750 with extreme horror. We had to manually create each user.

    Of course I was simply a lowly programmer working under the direction of our totally incompetent network admin--maybe there was an easier way and she missed that topic in the training the week before.

    What you really need is a requirements analysis. Exchange is a totally different thing than, say, Sendmail. Analyzing what you need will tell you which to go with. For instance, do you need public folders, scheduling, etc? If so, maybe use Exchange. Do you need configurability, speed and Internet email? Then you want not-Exchange.
    Put Hemos through English 101!
  • by Bryant ( 25344 ) on Thursday July 29, 1999 @01:23PM (#1776179) Homepage
    Upwards of 30K shell users, four Sparc 2s, SunOS 4.x, sendmail. And a lot of email. Our only big issue was the number of files in /var/spool/mail, which we coped with by going to Network Appliance NACs.

    We noted that directory lookups got worse in a distinct knee -- i.e., we had no problems for a long time and then we hit a magic number and things went all to hell. I do not know offhand how well linux or Solaris deals with directory lookups, but you could test easily enough.

    The thing you didn't tell us was what the volume would be like; the number of users matters for the mail spool but the number of email messages matters for the CPU usage... I suspect that you won't need a very heavy box, though. Email is cheaper than you might think.

    Oh. Run a DNS server on the mail hub, to avoid a lot of lengthy DNS queries on some other poor machine. Flush the cache daily.
  • Compaq / Digital professional services deploy and manage virtually all of the largest Exchange deployments- once you get above a certain deployment size, the requirements for maintaining the system require extremely specialized and arcane knowledge that (apparently) only they have. MS actually has structured the MS Exchange support contracts so that above a certain deployment size, you pretty much have to use Digital, or you won't get any support from Microsoft.

    So, unless you're willing to fork over the $$$$ for consultants from Digital to come and build the whole thing for you, I'd avoid Exchange like the plague for a project this size.
  • Why not to use sendmail with its local default mailer:
    1. The mbox format it uses is very nice for moving things around, but don't forget, if one acct gets bogged down, it gets blocked due to file locking problems. (if you use the default local mailer). Multiple mail files are nicer. May run out of inodes quicker if you aren't careful.
    2. Its ruleset bogs things down just a bit. Significant if you want to get more than 10k emails out in an hour. (I haven't really benchmarked it yet.) Power versus speed, configurability versus mail handled per sec.
    3. Sendmail is a big program. Qmail is smaller and more modular in the sense. The operating system's process scheduler can handle things better than sendmail's internals. I've had server loads of 10 with higher traffic on a dual 300mhz machine.
    Why not to use qpopper
    1. To download your mail, a second copy of your mail spool file gets made so that qpopper can sort out which mail you wish to keep. Effectively you get only 50% of the diskspace.
    2. All users must exist on the system. Bad system administrators (like at my old job) would make home dirs for all users, leaving ftp open at times. Virtual local users kick butt.
    There is your reliable software. For network stuff, I would highly recomend FreeBSD, but Linux would do fine. I would recomend qmail as it is both a popper, mta and local mailer. It doesn't give the problems above.
  • by mbeattie ( 30768 ) on Friday July 30, 1999 @12:23AM (#1776207) Homepage
    The talk was "The Design and Implementation of a Large Scalable Mail Server". It's about the mail cluster I set up here for Oxford University and it sounds similar to what the original request was for. We have about 30000 users. I successfully argued against MS Exchange and designed and built a completely Open Source solution based on a Linux cluster with 250GB of disk, UW imapd/ipopd, Exim (MTA) and an Apache/mod_perl-based web to mail gateway that I wrote called WING. The two Solaris nodes in the cluster were there for political reasons and are being replaced by Linux boxes within the next few weeks. There is a WING web page [ox.ac.uk] and mailing list which includes a link to the PostScript slides [ox.ac.uk] of the talk. The slides will also be shortly be available from UKUUG [ukuug.org].
  • by ibbieta ( 31756 ) on Thursday July 29, 1999 @01:27PM (#1776211)
    Yes, please, for your sanity, do not use Exchange unless you have to. It is large and cumbersome and requires a large server with expansive drives for even one hundred users.

    I use and maintain an Exchange server (well, three) and the main server consumes 10 gigs of a harddrive and all of a 333 MHz Pentium. This is for about 200 users and most are not that active.

    Besides the hardware overhead there are other negatives to Exchange. Namely, it does not route internet traffic well, it has poor error reporting, and it "clusters" badly. I'll take each point one by one.

    My company has affiliates in small offices around the world and they have neither the on-site resources or talent to maintain an e-mail server so these offices use our Exchange server as POP3 and SMTP. This creates an open relay and all attempts to close the relay have met with stiff opposition -- users complaining they now have to use a password, cannot remember what domain they are on, and general users resisting change. At the moment, Exchange has no true "Back Office" solution for this problem and I would have to personally configure all of our affiliate offices if I want to completely secure routing.

    The error reporting come down to this -- either you log all of the messages passing through Exchange or none of them. I wanted to log the messages that caused errors for obvious reasons and after about 4 days noticed the drives filling up with archives all all the messages, not just those messages generating errors. Microsoft admits this is a problem but there is still no fix, at least not in SP2.

    And finally, "clustering". I'm not talking about true clustering but instead about using multiple Exchange servers to distribute the load somewhat. We have two e-mail domains and wanted to start putting people on the second domain to balance the load. Each server runs fine on its own but for some reason they hate talking to each other. The replication services keep stopping (pausing, really) and site connector is more frustrating than helpful.

    I have not had many problems with our Exchange server otherwise. It runs forever and reliably. It has the longest uptime of any of our NT machines, only needing a reboot every month or two. However, I'd think long and hard before accepting a job caring 25,000 user's e-mail if the server were NT. Anything over about 1000 users you should look elsewhere if you can.
  • I'm currently working on the feasability of a mail cluster for 100 000 accounts. It's not done yet, but our various experiments gave us various answers.

    We use exim, Qpopper with mysql patche, mon, fake and rsync. Each base box hold 88 GB of data and are fully duplicated (double delivery with exim, and further syncronization with rsync). The switch between a main base box and his double are handled by mon and fake. A hot spare then reconstruct a new double, delivery and popper deletions are blocked during the reconstruction.

    Two problems aren't solved yet:
    - raid 1 between boxes
    - imap

    I hope that imap will work when nfs locking will be reliable. For raid 1 over boxes I have a very tiny hope that nbd could be a solution.

    Anyway, we made some tests, and it somewhat works already. We are now tuning various parts and writing procedure to handle the beast and react to failures (our current estimate is one major but handable failure every month).

    If you have ideas of working solutions for my 2 problems don't hesitate to share :-)

  • Handling a 25,000 active user base on one machine might be a problem for intel machines, and (dare I say it), most Open Source OS's.

    Solaris will do this, but you will probably need to run it on a _big_ box, like a Sun Ex500 class machine with about 8 or more processors. And get their SIMS product, too, it's pretty well optimised for the high end. Other high end commercial unixes like AIX and IRIX will no doubt scale this far as well.

    If you are able to go distributed (ie, the organisation is easily divisible geographically), then something like Linux or FreeBSD with qmail or smail will probably cut it.

    Beware that exchange servers offer a fairly high level of integration with Outlook, which a product based on open standards will not be able to deliver.
  • by Festus ( 37143 ) on Thursday July 29, 1999 @02:57PM (#1776228)
    To be perfectly blunt, to implement Exchange like that would be *INSANE*.

    First of all, suggesting to implement an NT solution for an organization of that size is already tempting your job security, but to actually do it?

    Assuming standard users and needs for this system, I can only recommend using a Lotus Notes/Domino system. If you've got the cash, there is simply no better solution out there, or even close.

    Run Domino (the server end of Notes) on several UNIX servers. Solaris (SPARC and x86), AIX, and HP/UX are all supported, with a Linux port (Caldera 2.3 (currently in beta) and Red Hat 6.0 will be supported, as well as SuSE 6.1 and Pacific HiTech) on it's way Q4 99 per DevCon.

    Notes has got all you'll ever need, and R5 simply blows away anything M$ has out there. You've got to pay for seats with Notes, but to tell you the truth, Exchange is free, and you get less than you pay for.

    Plus, your users can run the Notes client on any Win32 they think is prettiest (please tell me you'll use NT and not 9x on the client end).

    Look at this [weightlessdog.com] for a guy in your situation who had to deal with Exchange.

    Some other really good links are here [sandia.gov], here [computerworld.com], and here:

    http://www.notes.net/50beta.nsf/7d6a87824e2f0976 8525655b0050f2f2/35BEC3BF6D717A3F852567120 07A435A?OpenDocument
    (problem with the last one, copy it and cut out the space that is stuck between the zero's, the href tag keeps putting it in! It is a great article though : )

    (TIP: Show the guys with the money those links so they know why you should use a Domino/Notes solution.)
  • Check out www.apexmail.com [apexmail.com]. they have over 50 000 active clients, running on a totally linux based system. (They use totally custom software). Their setup includes a dual PII 450 file server with a 150 GB RAID (on a Mylex RAID controller). The entire public site runs on 4 or 5 single PII 450s, all on a switched 100BaseT network.
  • FWIW, FreeBSD takes of the web frontend and Solaris handles the database which stores all the mail. To my knowledge it was never anything _but_ FreeBSD & Solaris. M$ tried, and quickly backed out NT because it just couldn't scale to something this size.
  • Having to still support an old network installation run by a bunch of idiots (they are attempting to implement a mostly micro~1.oft shop), I can tell you that outlook doesn't scale to more than 2000 users before the maintenance starts to become a headache.

    This is a large client trying to implement a server farm of 20+ NT machines, each server supporting 600-800 users, and combining the whole lot into a coherent whole. Fortunately I only have to fix their poor network designs. The team of administrators now numbers more than 50, most are MCSEs, none less than 5 years experience with Micro~1.oft products. They are tearing their hair out on a daily basis. Complaints number in the hundreds every day, and thats just the users who haven't given up completely.

    My advice is to start looking at the larger commercial products, possibly Netscape's server. Get a reputable vendor to support it.

    If you look at open source systems, start with OpenBSD and NetBSD.

    Divide your system up between the MTA doing delivery/reception of the messages, and the MTA serving the users. Its ok if email to the outside world goes down for short periods of time, its almost expected. But if users cant get to their mailbox 100% of the time, you will look bad.

    You also need to look at managing more than 32000 or 65000 users in the future, remember that various *nixes have either 15 or 16 bit UID fields. You should make sure user accounts/authentication/logins are separate from any UID system on any machine type. This means getting some kind of medium sized DB, and tying it into your auth and login schemes. Others have done it, its not that hard (look at AOL with 10million+ user accounts)

    the AC
  • No matter what solution you pick (or gets chosen for you) would you please report back to us with how it went? It would make a great case study either whether or not MS can handle a true enterprise level application or how well FreeBSD/Linux/whatever handles it.

  • Sigh...

    I work for the second (or third, I forget) largest Sun reseller on the east coast. I have set up mail systems for several fortune 100 companies with 10k+ users. Anyone recommending a *500 series machines for this number of users is insane, especially with more than 2 processors.

    None of the MTA's out there are capable of making use of an SMP system and so anything more that 2 processors is really going to go to waste. (This is not entirely true however disk bottlenecks are far more critical to system performance)

    I have also set up mail systems based on FreeBSD. My last box was a Dual p][450 with 2 gigs of ram and a pair of mirrored seagate cheetah system disks. The machine has a pair of SmartRAID IV caching RAID controllers from DPT with 64 megs of cache. Connected to each controller is a series of seagate cheetah hard drives in 4 DPT Drive cabinets (per controller). The controllers run RAID 0+1 for maximum performance and reliability.

    The OS itself has been configured with a large MAXUSER limit and it is running Postfix using an LDAP server and running UW imapd (all hacked slightly to work together more smoothly). The system is also configured with softupdates to imporve FS performance. This system is as fast as anything I have ever used. It is easily capable of handling 5 million messages a day. This is over 200 messages a day per person on a 25k user system. Needless to say this system continually outperforms my expectations.

    I have set up similar systems on Sun hardware but the high cost of that hardware makes these solutions prohibitive. It also makes it a lot harder to get a system to do what you want it to do if you cant hack the source code a little.

    In the end a freeware solution like FreeBSD is more than up to the task of handling a large mail system like this. The only issues are proper configuration of this system. This issue applies to Solaris on sun hardware as well so it should not be mistaken as only a freeware problem.
  • One thing to watch out for regardless which solution you use is that (last time I looked) linux (or is it ext2?) is limited to 16-bit uids. There's ways to get around that; I just wish we'd considered it when we started.

    A good way to get around this is using qmail's LDAP patch. This way, you only need qmail's own local users. You should be able to convert your existing users to LDAP with no problem.

  • Currently the ISP I work has 50,000+ mail accounts on a multiserver solution... NetApp 720 for the file store on a private segment, A DellPowerEdge 2300 for the incoming mail server, and a 450 Pentium II with 256M ram for the POP box, MySQL POP Authentication tables, and a standalone MX20/Relay on another Micron Pentium II (I believe, haven't had to mess with it much)...

    If you need IMAP, it gets tough... Except for IMAP I'd recommend Qmail.. it's the most robust thing, besides the NetApp that we have.. With NetApp and a RAID0 backed queue drive it screams...

    You could all of the above with Penguins or VARs for pretty cheap... at guess 10,000 excluding the NetApp... If you use a beefy linux box with a fast raid 5 for the NFS server back end you'll also allow your servers to "load gracefully" ;-)

    If you need IMAP but on a single domain, use the UW IMAP server... It even comes as an RPM and looks great... If you need multiple virtual domains like we do... IMAP looks pretty grim...

    As it is when we go to web based email it looks like we're going to have to do a WebBased POP client...

    Careful though, IMAP can get *WAY* more abused though... With IMAP you have the tendency for people to park and use more space... With POP it's just grab and go..

    Resource wise POP is a better bargain and most clients can deal with it just fine... IMAP isn't worth the server load IMHO... Use qmail anyway ya can... ;-)
  • Ok I'm taking issue with this one. I'm a big fan of Linux and FreeBSD the rap you're giving Exchange here is not accurate.

    First off I have 1200 users on a dual processor 16G hard drive, 512mb ram system. It has run 372 days without crashing/reboots/etc. Mail delivery is fast enough that it might as well be a chat room at times from people sending emails and replying so fast.

    It has taken a good 4 waves of the Melissa virus without crashing or even blinking hard.

    Other than adding uses and deleteing users there is NO, I reiterate- NO, other work done on it. The damn thing just runs. Period. No extra maintenance at all.

    Yes the license cost blows goats. Yes MS does too. No Exchange isn't all that bad for a large scale environment if the people setting it up have a clue.
  • At the last Usenix conference a paper was given describing a very high volume mail delivery system called "Meta".

    The paper is available here [stacken.kth.se] (in postscript).

    At the talk I had the impression that the softwware was free. I cannot find it on their (skimpy) web site though.

    From their description, 25,000 users wouldn't begin to make it sweat.

  • by thomh ( 73668 )
    i work for an isp in the uk and we run our mail on mcis (microsoft's commercial internet server) in conjunction with LDAP and SQL. it works fine with around 300,000 users (adminttedly with clustering, but allunder nt using compaq h/w).

    i would recommend against using ms exchange as i know many people who have had loads of trouble with it.

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