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Date:      Tue, 10 Aug 1999 00:03:53 -0400 (EDT)
From:      "Crist J. Clark" <>
To: (Mark Einreinhof)
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: Mail server question
Message-ID:  <>
In-Reply-To: <000201bee2dd$2e94b520$> from Mark Einreinhof at "Aug 9, 99 10:05:20 pm"

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Mark Einreinhof wrote,
> Ok, help me understand the difference in mail servers...
> Sendmail handles SMTP traffic, but doesn't handle POP. Is that correct? Does
> Sendmail handle IMAP or is that an add on?

Just like POP, IMAP is a separate protocol. You often get POP and IMAP
from a single package, however.

> If I install UW's IMAP software does that mean I have SMTP/POP/IMAP separate
> from Sendmail, or does it mean I just added POP/IMAP to the server and
> sendmail handles SMTP?

Yes... Kinda. sendmail is a Mail Transfer Agent (MTA). sendmail is
what gets email from your "site" to someone else's "site." Now how a
user gets mail to their Mail User Agent (MUA) is up to the people at
the other site. They might use POP or IMAP, or even just good ol' elm
or pine reading straight off of a mailspool created by sendmail's
local delivery.

The UW IMAP package provides POP and IMAP. It does not really do
SMTP. It is what a MUA (say fetchmail, Netscape, or M$ Outlook) would
contact to grab mail from the server. When the MUA wants to send mail,
it typically will use SMTP itself and go directly to the sendmail MTA
for relaying. IMAP or POP is not involved in the sending of mail.

Get it, got it, good.

It seems complicated, but this is because each piece of software has a
specific job to avoid each one from getting too bloated (well,
sendmail...). Once you figure out what each does and how they fit
together, it is quite simple. The alternative is making something that
is meant to be an end-all-be-all mailserver that becomes a hopeless
snarl, e.g. M$ Exchange. 
Crist J. Clark                 

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