Date: Wed, 24 Apr 2002 11:32:19 +0200 From: Brad Knowles <brad.knowles@skynet.be> To: fcash@bigfoot.com, Nik Clayton <nik@freebsd.org>, chat@freebsd.org Cc: "Freddie Cash" <fcash@mail.ocis.net> Subject: Re: IMAP server recommendations Message-ID: <p05111704b8ec29a069cd@[10.0.1.46]> In-Reply-To: <3CC5F3C5.17529.66E7800@localhost> References: <3CC5F3C5.17529.66E7800@localhost>
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At 11:52 PM -0700 2002/04/23, Freddie Cash wrote: > The easiest to set up and use is UW-IMAP. Runs via inetd and is about > as easy to install/run as telnetd. However, it doesn't scale beyond > about 100 users, and can be slow with large mailboxes. Agreed, UW-IMAP is the way to go for small-scale boxes. It's designed to be maximally backward-compatible, supporting virtually all known mailbox formats (including 7th edition "mbox" format), and both local users (accessing the mailbox directly) and remote users (accessing it via IMAP). As a result (and as you noted), it does not scale well. > The hardest to set up and use (IMO) is Cyrus. There's virtually no > documentation on it and it is in a constant state of flux. Plus, the > whole SASL thing is just mind-boggling. However, those that have put > the time in to make it work swear by it, so there must be something to > it. I'm told that Cyrus is a pain, and there is certainly a lot to build and install for it. However, if you want a scalable IMAP server, the best available is either Cyrus itself, or a commercial product based on Cyrus (such as the MessagingDirect product). The Cyrus concept is to run as a "black box" mail server that allows *ONLY* IMAP as the mailbox access method, and of course you need some sort of method to store messages as well. By eliminating support for all that unnecessary stuff (especially local users, all the other mailbox formats, etc...), Cyrus can be very fast, and can scale very, very well. All large-scale IMAP mail servers that I know of are running either Cyrus or some product based on Cyrus (such as MessagingDirect). But those only go up to two or three hundred thousand users -- I'm not aware of anyone in the world running an IMAP server handling much more than this. I recommend that anyone interested in this topic buy a copy of _Managing IMAP_ by Dianna and Kevin Mullet, published by O'Reilly, ISBN 0-596-00012-X, <URL:http://www.oreilly.com/catalog/mimap/>. > Somewhere in the middle is Courier. This can be installed as either a > full-blown e-mail server with IMAP, POP, and SMTP, or as just IMAP. I've never quite bought into the Courier model. > Fairly straightforward to setup and use, and is supposed to scale > nicely. It uses the MailDir format which is supposed to be the most > network friendly (for mailboxes stored via NFS or access by more than > one process at a time). I certainly don't buy Maildir. Among other things, it trades synchronous meta-data updates for "NFS-safe" operations, playing games with the semantics of the Unix creat() call. However, we know from experience that the single most important bottleneck to *REMOVE* on MTAs and other mail servers are precisely those same synchronous meta-data operations, so it seems to be a non-sequitur to me. Moreover, Cyrus and MessagingDirect prove that you can be NFS-safe *AND* eliminate as many synchronous meta-data operations as possible, through pulling file locking into the database. > If you need it right now, I'd suggest UW-IMAP (especially with only 2 > users). Once that's up and running, you'll have time to play with the > other ones, if needed. Agreed. Myself, once I get around to setting up my own personal mail server (I do not yet have the hardware or the co-location service provider), I will be installing Cyrus, but that's just because I believe that I need to eat my own dog food. -- 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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