SPF records in reverse zones?

Dan Mahoney dmahoney at isc.org
Wed Dec 5 23:52:43 UTC 2012

On Thu, 6 Dec 2012, Karl Auer wrote:

> This may be a silly question, but are SPF records supposed to be
> supported in reverse zones? I'm thinking of a mail server that has no
> entry in the DNS.

Well, most mail servers will reject such a server (i.e. one with NO rdns).  
However, there's another possible interpretation of your request.

SPF records go in the zone of the envelope-sender.  So if your server's ip 
is, and your mail address REALLY is 
bob at, then the reverse zone would also need to 
have an MX and possibly an A record, in order to route mail to it, which 
goes a far cry from being "a server that has no entry in the DNS".

I can't even imagine what spamfilters would think of such an address. :)

-Dan Mahoney

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