Date: Wed, 10 Jul 2002 01:26:56 +0200 From: Brad Knowles <brad.knowles@skynet.be> To: cjclark@alum.mit.edu, chat@freebsd.org Cc: "Crist J. Clark" <crist.clark@attbi.com> Subject: Re: Mail Software Used by ISPs Message-ID: <a05111b41b9511a960f85@[10.0.1.15]> In-Reply-To: <20020709152544.B40078@blossom.cjclark.org> References: <20020709152544.B40078@blossom.cjclark.org>
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At 3:25 PM -0700 2002/07/09, Crist J. Clark wrote: > I am interested in information on what software small, medium, and > large ISPs use for email services. When I refer to "email services" I > mean SMTP, POP, IMAP, web mail interfaces, and the back-end > administrative tools. Do many/most ISPs use big, expensive enterprise > tools for this? Piece their own systems together using various > commerical/free tools for the different parts? Or do they roll their > own almost top to bottom? The folks at companies like Software.com will try to convince you that the largest ISPs in the world use their systems. That's not true. You can throw dozens of Sun E4500s at something like Software.com and serve only about 100k users. At Belgacom Skynet, we served almost a million users with sendmail and a modified local delivery agent (to handle hashed directories), a modified version of QPopper (matching the hashing algorithm used in the local delivery agent) or a modified version of Cyrus. This was running on a pair of Sun E420Rs, each configured with four 450Mhz UltraSPARC II processors each, 4GB of RAM, and connected via FibreChannel to an external dishwasher-size RAID array (re-badged Hitachi DF400s). You can read more about the architecture that I recommended we replace this with at <http://www.shub-internet.org/brad/papers/dihses/>; ("Design and Implementation of Highly Scalable Mail Systems", presented at LISA 2000), based on front-end SMTP servers running the commercial Sendmail MTA (with anti-virus scanning and anti-spam provisions via the Milter interface), back-end Sendmail Advanced Message Servers, webmail systems, etc.... This architecture should easily scale to handling at least a million users (larger than any other IMAP mail system in the world that I know of), and should scale to handle at least ten million users or more. I was interested to find that this architecture was implemented almost verbatim by a very large mail outsourcing company in Scotland, down to the recommendation of a particular family of Hitachi FibreChannel disk storage devices. For POP3-based sites, the largest mail systems in the world that I know of are running an architecture along the lines laid out by Nick Christenson in his paper "A Highly Scalable Electronic Mail Service Using Open Systems" at <http://www.jetcafe.org/~npc/doc/mail_arch.html>. Note that Nick was my co-author for the paper I presented at LISA 2000. > I have experience doing email for small and medium corporate sites (in > the 100's of internal users), but the particular project I am working > on is for customers, not internal users, and could quickly balloon > from the few dozen on the current demonstration system to a few > thousand. Any firsthand info or pointers to more information would be > greatly appreciated. A few thousand users is no problem. See Nick's page at <http://www.jetcafe.org/~npc/>; and my page at <http://www.shub-internet.org/brad/papers/>. We've both been professional consultants in this business for a long time, and if we can't help you, we should be able to point you at people who can. You may also be interested in Nick's book _sendmail Performance Tuning_ (Addison Wesley Professional, ISBN: 0321115708), to be published in September. -- Brad Knowles, <brad.knowles@skynet.be> "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, Historical Review of Pennsylvania. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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