Date: Tue, 22 Jun 2004 10:09:55 +0100 From: Andy Holyer <andyh@hhbb.co.uk> To: Martin McCormick <martin@dc.cis.okstate.edu> Cc: freebsd-questions@freebsd.org Subject: Re: Sendmail for Large Sites Message-ID: <ED6C4183-C42B-11D8-9882-000D93511A6A@hhbb.co.uk> In-Reply-To: <200406181113.i5IBDh1E035926@dc.cis.okstate.edu> References: <200406181113.i5IBDh1E035926@dc.cis.okstate.edu>
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On 18 Jun 2004, at 12:13, Martin McCormick wrote: > How well does the administration of Sendmail scale up to sites > serving as many as 25,000 users? > > At this moment, everything is more or less on the table, but > what I envision is 25,000 work stations or so, each using Microsoft > Outlook and several Sendmail servers serving the multitudes. We might > use dns-based round-robin load balancing for all I know. This is all > simply a mental exercise at this point, but the hardware is already in > place running a commercial package which may have to be replaced if it > can't be made to perform properly and soon. > > I am mainly interested in Sendmail's capacity at this time in > order to suggest it as a possibility if it is realistic to do so. > > There are other considerations such as the facts that all > incoming and outgoing messages are checked for malicious attachments. > ldap is used to drive the setting of customer mail delivery > preferences and even their user ID choice. > > To use an American vernacular, it is a tall order. I'd suggest you look at Postfix, a free alternative to Sendmail produced at IBM's TJ Watson Labs. The advantages of Postfix are as follows: 1) It's not sendmail - it acts identically, but shares no code, so it's immune to the sendmail exploits which sometimes appear in the cracker communtiy (rather like my iBook accepts viruses, and then watches as they fail to execute, being written for the wrong OS and processor) 2) Sendmail is written as a single monolithic program, so each executable sendmail uses a big chunk of memory to operate. Postfix is written as a network of small programs each of which does a single thing. This has a number of advantages: different components can be reinforced as need be to respond to minute-to-minute changes in load; the overally impact on system resources is smaller; and it's easier to spread processing power over multiple threads, processors and even hosts. Also if the spooler falls over the rest of the system carries on, so you don't have a total panic. 3) Sendmail's configuration file is written in an obscure style which has sent many brave souls to their deaths (recent versions are improved, but still AFAIK far from crystal clear. Postfix's configuration files are huge, but you colud at least read them out loud and they'd make some form of sense. Just my 2p. --- Andy Holyer, Technical stuff Hedgehog Broadband, 11 Marlborough Place Brighton BN1 1UB 08451 260895 x 241
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