Sendmail for Large Sites

[Charles Swiger]

On Jun 18, 2004, at 7:13 AM, Martin McCormick wrote:
> 	How well does the administration of Sendmail scale up to sites
> serving as many as 25,000 users?

Sendmail is fine for the task, as the main issues to be concerned about 
have more to due with user-agents reading the mail (as in, your POP and 
IMAP servers), and how mailboxes are kept, than with the MTA and 
SMTP-level issues.

> 	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.

Sure, sendmail can solve the problem as specified.  Let me mention a 
book by Nick Christenson, "SENDMAIL Performance Tuning", ISBN 
0-321-11570-8, because it would certainly help you, and because it has 
a section worth quoting here on page 10:

	---

1.7 Email System Profiling

More times than I care to remember, I've had a conversation with 
someone trying to specify an email system that went like the following:

Them: I need to build an email server using Sun equipment that will 
handle X number of users.  What hardware should I buy?

Me:   Well, that completely depends.

Them: On what?

Me:   On their usage profiles.  How many messages does each person send 
and receive each day?  What is the average message size?  How fast is 
your Internet connection?  What percentage of your peak day's total 
traffic occur during the peak hour?

[ ... ]

When it comes to email servers, it seems that just about the only 
information anyone can obtain from a prospective client is the number 
of users.  Unfortunately for performance purposes, this figure is just 
about the least useful metric for evaluating email service load.

> 	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.

Cyrus' IMAP and SASL software will play friendly with LDAP, as will 
sendmail itself.  amavisd + clamav is a good solution for scanning mail 
for viruses and the like.

You should strongly consider using maildir rather than mbox-style mail 
delivery.
You might want to consider postfix instead of sendmail.

-- 
-Chuck