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Sender Policy Framework


The "ptr" mechanism (edit)


The hostname or hostnames for the client IP are looked up using PTR queries. The hostnames are then validated: at least one of the A records for a PTR hostname must match the original client IP. Invalid hostnames are discarded. If a valid hostname ends in domain, this mechanism matches.

If domain is not specified, the current-domain is used.

If at all possible, you should avoid using this mechanism in your SPF record, because it will result in a larger number of expensive DNS lookups.


"v=spf1 ptr -all"

A domain which directly controls all its machines (unlike a dialup or broadband ISP) allows all its servers to send mail. For example, hotmail.com or paypal.com might do this.

"v=spf1 ptr:otherdomain.com -all"

Any server whose hostname ends in otherdomain.com is designated.

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Last edited 2006-12-11 22:58 (UTC) by Julian Mehnle (diff)