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Subject: Re: multiple mail servers
From: Brad Knowles (blkskynet.be)
Date: Wed Jun 07 2000 - 19:11:43 CDT

At 8:58 PM +0200 2000/6/7, Rask Ingemann Lambertsen wrote:

> It can be done, of course, but why? Then you lose the potential gain in
> availability and the extra performance (assuming you have a need for it),
> and you gain nothing, as far as I can tell, by separating incoming mail
> from outgoing mail.

        You want to split incoming from outgoing mail servers, so that
you can do different things on them.

        For example, the incoming mail servers don't need to implement
SMTPAUTH or TLS, while the outgoing mail servers should (since these
are the machines your customers would be connecting to in order to
deliver mail to the outside world).

        In addition, the outgoing mail servers should implement the ORBS
black list (in case some of your customers are open relays, you don't
want to get your own machines added to the ORBS because you are being
abused as a third-party relay), while the ORBS is screwed up enough
that you *really* don't want to implement it on the inbound servers.

        Finally, if you need to add more inbound servers, you can do that
without having to integrate them into the outbound system. The
converse is also true -- you can quickly throw up a new outbound mail
relay with just postfix, and you don't have to spend more time
putting together the hacked POP3/IMAP server on it, putting the
hacked-up ODMR/ETRN/fingerflush daemon, or anything else. This also
allows you to use a larger number of much cheaper systems for the
outbound mail servers, while concentrating more horsepower and money
onto a smaller set of inbound mail servers -- if that's the way you
want to go.

        Trust me, you really do want to split these functions. Having a
"one machine does all" solution simply does not scale -- I speak from
experience. 

--
   These are my opinions -- not to be taken as official Skynet policy
======================================================================
Brad Knowles, <blkskynet.be>                || Belgacom Skynet SA/NV
Systems Architect, Mail/News/FTP/Proxy Admin || Rue Colonel Bourg, 124
Phone/Fax: +32-2-706.13.11/12.49             || B-1140 Brussels
http://www.skynet.be                         || Belgium