With the growing number of SPAM-sending hosts, administrators apply more and more rules to block as much SPAM as possible. These rules are usually requirements of different RFCs, so a company’s system administrator should have no excuse for the fact that he does not follow the rules.
Some administrators may not be aware of these RFCs. So I collected a few usefull links over here.
Yahoo seems to apply the RFCs very tightly, so dear lazy sysadmins don’t be surprised. Yahoo references this howto for the “lazy” ones between you:
Is my DNS a mess… Most probably, Yes!
And Comcast includes this one in the SMTP error message:
Some useful links for those who want to change their setup:
RFC-Ignorant.org
Time to fix your system…