Thursday, June 30, 2016

smtp - Multiple mail servers and reverse DNS



If I have three mail servers MS1, MS2 and MS3 all with different IPs but share the same domain name (exampledomain.com) and I use an SPF record to specify them, how would reverse DNS work on the server receiving mail from any of my mail servers since each of them would resolve to a different IP?
Or would the receiving server have to check against the SPF records instead?


Answer



Never name your mail servers (or any other server) with the naked domain name. This will break a lot more stuff than forward confirmed reverse DNS lookups.



Each server should have its own unique name which is a subdomain of your domain, and for which the reverse DNS points back to that name.



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