SPF

A Sender Policy Framework is a method whereby the owner of a domain can choose to specify which mail servers people who claim to be sending mail from that domain are allowed to use.

Vex.Net respects domains publishing SPF information. What this means is that all incoming mail checks to see if the domain in the from address has published SPF directives. If they have Vex.Net makes sure that message is being sent from one of the mail server addresses that that domain has specified as valid.

In short, it means people can not spoof mail as coming from a domain which participates with SPF.

Vex.Net itself does not publish SPF information at this time. Vex.Net only, on incoming mail, respects the directives of domains which do.

Many very large ISPs are using SPF now to prevent people from faking email to appear to be coming from them. While by no means a complete solution to the SPAM problem, it is amazing how much it does eliminates.

Note that there could be problems if you forward your email through a third party that does not properly implement SPF. If they publish an SPF record but forward mail rather than remailing or rewriting the headers it will be rejected by Vex.Net. See Sender Rewriting Scheme for a discussion of this issue.