Multiple A records and reverse DNS

Blake Hudson blake at
Fri Mar 18 20:20:40 UTC 2016

Tom, when your mail server establishes a connection to another host, the 
receiving host will likely automatically check the PTR record of the IP 
address your server used as it's source address. This PTR record should 
have a corresponding A record that points to the same IP address that 
was looked up in the PTR record. This is sometimes referred to as a 
"verified" hostname. Without this, receiving mail servers may sometimes 
log your rDNS as unknown, which can look spammy to subsequent spam 
filters. You can have any number of other A records that point to your 
server, they are irrelevant to PTR verification.


Your reverse zone:    IN    PTR

Your zone:    IN    A    IN    A    IN    A    IN    CNAME

All the matters to PTR verification is that has a PTR record and 
that PTR record exists as an A or CNAME that eventually points back to

As others have pointed out, this is best common practice for outgoing 
mail servers aka mail relays; However, I generally recommend having 
valid PTR records and having matching forward records for any servers. 
Maybe it's just me, but most of my server's send email - even MX servers 
(they do create NDR notices from time to time).


Thomas Schulz wrote on 3/17/2016 8:53 AM:
> This is not a BIND question but I hope people here will know the answer.
> We are switching service providers and I understand that many email SPAM
> prevention systems insist on the reverse DNS matching the forward DNS.
> If I have two A records for our mail server and the reverse record matches
> one of them, will that be good enough. Or will the fact that the other A
> record does not match cause trouble.
> Tom Schulz
> Applied Dynamics Intl.
> schulz at
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