From: "Justin Mason" <[EMAIL PROTECTED]> > - - if a spammer were to use a hostname like > "jm_at_jmason_dot_org.spamdomain.com", they get a free backchannel to > verify that I was (a) using SpamAssassin to filter to my mail, and (b) > that that address is valid. So blindly resolving the full hostname was > judged as unsafe. However, replacing hostname portions with another > token is not useful: assuming that "jm_at_jmason_dot_org.spamdomain.com" > will have the same A as "spamdomain.com" or "www.spamdomain.com" is > naive and easily evaded.
Seems many already do with base64 (or other) encoded gibberish in front of the spamdomain.com. {o.o}