Mailing List Message #94731
From: Uwe Baemayr <>
Subject: Re: Question about backup server/relaying
Date: Sat, 12 Apr 2008 15:52:13 -0500
To: CommuniGate Pro Discussions <>
X-Mailer: Pegasus Mail for Windows (4.41)
Hi Stefan:

On 12 Apr 2008 at 15:03, Stefan Seiz wrote:

> On 12.04.08 02:08, Uwe Baemayr <> wrote:
> > Our MIS department was planning to change the MX record just before turning
> > off the server/starting the move.  However, I believe, because of
> > propagation relays, that may cause senders who have the old MX record cached
> > to queue mail for the old IP, which will never be active again, and that
> > will cause us to bounce email.
> Why not already add a secondary MX Entry with the NEW IP now already, and
> then, once the move is complete, make it the ONLY MX and delete the MX with
> the old IP. That way, any properly configured mailserver should be able to
> deliver to whatever IP will be functional at the moment.

That was my original thought, but I was concerned about the span of time
when neither server is functional -- whether mail servers would retry all
MXs on each delivery attempt or queue on the first forever.  I had the
impression that once CommunigatePro resolved an MX record, it just queued
the message for a particular IP.  This is based on an experience (probably
back in the v4 days) when I had a bunch of mail in the outgoing SMTP queue
for a defunct server and it didn't get delivered even after the MX record
was fixed.

> In any case, set the TTL for your MX Records to a low value (like one hour)
> at least a week in advnce of the move.

That's great advice and it will be done.

> Using your secondary Server as backup MX is surely better. Allthough you'll
> receive lots of spam to none existing accounts on it (as the backup can not
> verify what addresses are really configured on your main mailserver).

Definitely a concern, since the second mailserver is registered with
senderbase -- I'd hate to screw up the organization's "email reputation"
with some ill-advised bounces.  However -- is it possible to force relaying
to occur on a particular IP?  If so, I could use one of the IPs in the
organization's IP range that's not currently used for email and it wouldn't
matter so much if it was blacklisted for bounces.

Thanks again!

--- Uwe

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