Postfix Backup mx configuration

Posted on 2010-11-26
Last Modified: 2012-06-21
Hi there.

I have a backup mx using postfix at the moment, it is set to route the primary mx of domains using transport mapping.

Is there a way I can tell postfix to deliver only to the primary mx rather than manually mapping it every time?

Thanks in advance.
Question by:alexanderfoti
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LVL 19

Expert Comment

ID: 34220559
In the DNS entries for the MX records use a high priority (smaller number) for the primary

Author Comment

ID: 34221487
I think you have misunderstood the question, or I have worded it badly.

At the moment, I already have domains with this postfix server as their second MX.

if I dont implement a transport map, the server will try to deliver to their primary mx, fail (As its down etc) then try to deliver to the second mx which is itself.

It will then go into a mail loop. To prevent this, I have transport maps setup to tell postfix only to send to the primary mx. Whilst this works, it means I need to add it in to the configuration everytime I add a domain.

Is there a way in the config of postfix to tell it to only send to the first mx?
LVL 19

Accepted Solution

bevhost earned 500 total points
ID: 34221558
The name that you use in the secondary MX, does postfix recognise that as itself?
eg if postfix is behind a NAT gateway, then the MX record will resolve to a IP address that is not bound to the postfix server.
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Author Comment

ID: 34221957
No - the server is behind a nat and doesnt recognise it as itself, but, another server I have that ISNT behind a nat behaves in the same way
LVL 62

Expert Comment

ID: 34226457
all mailers should be identical.
some use lowest order mailer to catch spam and make dynamic blacklisting.
LVL 19

Assisted Solution

bevhost earned 500 total points
ID: 34226596
Why do you need a backup MX?
Is the primary connected by dialup? or some other non permanent connection?

Why not allow the mail to queue on the sending MTA?
At least the sender will have some chance of knowing that the mail is not beling delivered yet.

As for why postfix is behaving this way I'm not sure, I would not configure this scenario for the reasons above.  In the MX records, do you use the actual hostname of the backup mx server, (ie the one with the matching forward and reverse DNS entries?) or are you using alias names from the domain you are doing backup MX for.?

Author Closing Comment

ID: 34295526
Thanks - The Backup MX's are provided as a service to prevent end users getting bounecbackswhen a client's site is down from non RFC conforming mail servers.

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