[Mailman-Users] Virtual sites

Brad Knowles brad at stop.mail-abuse.org
Thu Sep 14 09:59:30 CEST 2006

At 2:13 AM -0400 2006-09-14, Jim Popovitch wrote:

>  OK, fair enough.  Back to Mailman, why is checking MX records (or at
>  least allowing specification of 2 or more SMTPHOSTS) a bad idea?  It
>  just seems to make good sense to me, considering failover, load
>  balancing, resiliency, etc.

There's nothing wrong in listing multiple IP addresses for the 
designated SMTPHOST.  DNS round robin and the way the TCP protocol 
works should take care of the failover issues without any added 
complexity.  If you wanted to put a Layer Four load-balancing switch 
in front of those mail servers, you could increase throughput and 
reliability even more.  If you wanted to make that Layer Four 
load-balancing switch fault-tolerant with an active-active failover 
mate, that would be yet another additional improvement.

However, speaking only for myself, Mailman does not need the added 
complexity of having to deal with looking up MX preferences, retrying 
DNS queries that are truncated because you tried to cram too many 
MXes into a UDP DNS packet, etc....

IMO, use the right tool for the right job.  These are all problems 
that MTAs have to deal with today, and how well they handle them (or 
badly), I don't think that this is a wheel that we need -- or want -- 
to reinvent.  Let the MTA do the job of the MTA, and let Mailman do 
the job of the MLM.

Now, that said, in a true and proper virtual hosting/domain 
environment, I've been thinking about this a bit more, and I can see 
that some people might prefer that each virtual host/domain should 
have a separate SMTPHOST setting.

The problem is that we don't have proper virtual hosting/domain 
handling within Mailman today, and I think it's generally a bad idea 
to retrofit one part of the overall solution without doing the rest.

Let's take care of this problem at the right time, when we're 
implementing a full and proper virtual hosting/domain environment 
within Mailman, and not try to put that cart before the horse.

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

  Founding Individual Sponsor of LOPSA.  See <http://www.lopsa.org/>.

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