SPF looks like it is worth supporting

With my Email administrator hat on, I have been looking at SPF lately.

SPF stands for Sender Policy Framework and is a mechanism whereby the owner of a domain can advertise that domain's policy on how it sends mail.

When an MTA recieved mail claiming to be from a particular domain, it can queries that domains policy and then make a determination on how likely it is that the from address is authentic. This information can then be used as input to a local policy on dealing with junk mail.

It is not possible with SPF to be certain that an address is faked as the mail may have come through a forwarding agency which left the from address unchanged. However it is possible in some cases to be sure that the address isn't faked and in those cases, white lists can be used to ensure that the mail you want gets through heuristic spam detection.

Once you have a high degree of confidence that you get the mail you want, you can be more aggressive in throwing out likely spam, without risking losing valuable mail.

The more people that are using SPF, the more valuable it will be.

Another value of the authenticity measure that SPF gives to return addresses is that challenge-response schemes become more usable. If you get mail from an address that isn't on your white list, you might send an email asking for some sort of confirmation that it isn't spam. If you do this without first checking the validity of the from address, you risk spamming other people.