At 14:00 3/10/02 +1200, Simon Blake wrote:
http://www.ietf.org/rfc/rfc2505.txt
To whit:
2.9. Verify "MAIL From:"
The MTA SHOULD be able to perform a simple "sanity check" of the "MAIL From:" domain and refuse to receive mail if that domain is nonexistent (i.e. does not resolve to having an MX or an A record). If the DNS error is temporary, TempFail, the MTA MUST return a 4xx Return Code (Temporary Error). If the DNS error is an Authoritative NXdomain (host/domain unknown) the MTA SHOULD still return a 4xx Return Code (since this may just be primary and secondary DNS not being in sync) but it MAY allow for an 5xx Return Code (as configured by the sysadmin).
Interesting.
It doesn't actually say that you must drop mail from nonexistant domains, but it certainly implies that those sending mail with nonexistant domains shouldn't be suprised if their mail does get dropped.
It doesn't get dropped, it gets rejected. If the MTA that rejected it was the one the end user was connecting to during the attempted send of the message (EG their ISP's outgoing server) their email client won't even be able to send the message - they will immediately get an error. Both Outlook Express and Eudora will display this error, not sure about others. However if the one rejecting it was the destination MTA then the sending MTA will not be able to deliver it, and will have to generate a bounce. Unfortunately, since the envelope-sender address is invalid, it has nowhere to bounce it to, except the postmaster.... (However, any other kind of "normal" bounces, like the destination address not existing will never bounce to the right place either, so the senders email configuration is "broken") Regards, Simon - To unsubscribe from nznog, send email to majordomo(a)list.waikato.ac.nz where the body of your message reads: unsubscribe nznog