Re: Scalable Mail solution with NAS

[Valdis.Kletnieks () vt edu]

On Wed, 31 Jan 2001 10:13:40 EST, chrisb () kippona com said:
> Is the number of mailboxes the key metric?  What breaks sendmail + "a
> very big disk"?  Isn't it the traffic?

The two biggest problems with very-high-volume servers and sendmail are:

1) You *really* need to use multiple queues and some sort of aging scheme,
so mail backlogged for dead hosts gets out of your main queue.  If a queue
gets too full, Sendmail exhibits bad O(N**2) behavior in sorting/running
the queue.

2) If you are serving mailboxes (as opposed to a Listserv-type machine where
the mail *leaves*), what can kill you isn't the sendmail, but the local
delivery program and POP/IMAP checks.  You get enough bozo users who have
set Eudora to check for new mail every 2 minutes, you'll get bogged down
no matter HOW fast Sendmail itself is.
-- 
                                Valdis Kletnieks
                                Operating Systems Analyst
                                Virginia Tech

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