SMTP has a security hole: any connecting client can assert any sender address. This flaw has been exploited by spammers to forge mail. Close the hole, and we can easily block spammers by sender domain.
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October 2nd 2003: A unification project has begun under the aegis of the ASRG: the authors of SPF, RMX, DMP, and other designated sender schemes are working together to produce a single proposal that gathers the strengths of the different approaches. Early adopters, please join the mailing list; the spec is very likely to grow additional features by the time we're done. [Privacy Digest]