different smtp host name

Jul 24, 2023

I'm new to PMG and would like to know if it's possible to set a smtp host name different from the machine's host name.

My current system involves 3 Sophos UTMs running as mail relays only. They each have a distinct name (mx2.d.tld, mx3.d.tld, mx4.d.tld) for management. I have my DNS set up with a single MX entry (mxprotect.d.tld) but there are 3 A and 3 AAAA entries for those machines. Each machine has the same smtp host name (mxprotect.d.tld). This should be mirrored by PMG, as well. First step would be to add the configured PMG to the mxprotect set and then step by step replacing the Sophos with PMG.

The first PMG has been set up and it does work fine, configured for 2 domains that I have configured to use the PMG only.

Regards, Haimo
I'd consider simply keeping the hostnames (and their reverse ptr entries) publicly with the distinct names
(That's not stopping you from having mxprotect.d.tld still point to all 3 A/AAAA entries)
In my experience such a setup should work fine (the various forward/reverse DNS checks make sure that the system trying to send a mail has a
consistent (helo_name),forward,reverse view of the world, which would be the distinct names) - I'm not aware of any system that
requires the system to have the same hostname as it's pointed to by it's MX(record)

If you still want to have the system show mxprotect.d.tld on it's various smtp-ports - you can adapt the corresponding postfix config parameters
using the templateing system:

and https://www.postfix.org/postconf.5.html#smtp_helo_name

are the 2 settings that I can think of right now (cannot 100% promise that those will be all - but should already provide a good starting point

I hope this helps!


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