This is a consideration for individual mail reception. In fact Yahoo was one of the major reasons I set up my own mail server because my isp uses realtime blackhole lists which temporarily block the yahoo servers and sends a hard bounce, which in turn caused Yahoo to suspend my group memberships. The try later response outlined in the greylist web page which Tanner referenced would probably not cause Yahoo! to do that.
The other problem I had was certain mailing lists which were also blocked via this mechanism. I'd try to sign up and never get the confirmation e-mail. This seemed to happen a log on sourceforge mailing lists. Of course, I don't suppose that we would really want to subscribe the Trilug mailing list to any Yahoo! groups, or other mailing lists would we? On the other hand, as Tevye in Fiddler on the Roof would say, I haven't seen very much if any spam relayed through the Trilug mailing list, have I been missing something? -- TriLUG mailing list : http://www.trilug.org/mailman/listinfo/trilug TriLUG Organizational FAQ : http://trilug.org/faq/ TriLUG Member Services FAQ : http://members.trilug.org/services_faq/ TriLUG PGP Keyring : http://trilug.org/~chrish/trilug.asc
