SMTP Server Callbacks, the Devil or a Godsend?
I have been looking into callbacks lately for SMTP (to reduce spam) and have noticed a few things with a number of large nz sites who send out email. A number of sites send from email addresses which don't exist. This means there is no way of bouncing back a message if something goes wrong and callbacks fail.. Large site such as trademe.co.nz,ferrit.co.nz,pxt.vodafone.co.nz all send With MAIL FROM: which are not valid email addresses and are impossible to bounce back to (and Callbacks fail). There are a few other small ones I've noticed.. but overall callbacks work fine. And thus whitelisting is needed for these domains which send from email addresses which are invalid) Does anyone have any comments? Suggestions? Why callbacks are the devil (or otherwise)? Why callbacks work really well..Anyone use using them? who they had to whitelist if they used them in NZ? Note: also noted there are a number of mail servers in nz which don't accept bounces at all (even to valid users) :-( rfc-ignorant.com anyone? Thanks Craig
Craig Whitmore wrote:
Does anyone have any comments? Suggestions? Why callbacks are the devil (or otherwise)? Why callbacks work really well..Anyone use using them? who they had to whitelist if they used them in NZ?
I recently came across a puzzling issue @SORBS which was reported as a host not using SORBS had trouble receiving messages where the rejection/bounce was reported as listed in SORBS... Turns out the callback was the issue - the receiving host was listed in SORBS, the callback resulted in the remote server that the user was legitimately coming from was using SORBS and was rejecting the callback based on the hosts listing in SORBS. The callback system could not detect the difference between no such user and any other type of error, so it rejected the message as a callback failure.
Note: also noted there are a number of mail servers in nz which don't accept bounces at all (even to valid users) :-( rfc-ignorant.com anyone?
FWIW every host that doesn't accept postmaster@ or abuse@ that I send mail to gets reported to rfc-ignorant.org, and that means all future mail from that host to the mail systems I manage is more likely to get classed as spam and therefore junked. Regards, Matthew
I'm glad Mathew is there to single handedly work out how the Internet should function. -----Original Message----- From: Matthew Sullivan [mailto:matthew(a)sorbs.net] Sent: Thursday, 27 July 2006 1:32 p.m. To: Craig Whitmore Cc: nznog(a)list.waikato.ac.nz Subject: Re: [nznog] SMTP Server Callbacks, the Devil or a Godsend? Craig Whitmore wrote:
Does anyone have any comments? Suggestions? Why callbacks are the devil (or otherwise)? Why callbacks work really well..Anyone use using
them? who they had to whitelist if they used them in NZ?
I recently came across a puzzling issue @SORBS which was reported as a host not using SORBS had trouble receiving messages where the rejection/bounce was reported as listed in SORBS... Turns out the callback was the issue - the receiving host was listed in SORBS, the callback resulted in the remote server that the user was legitimately coming from was using SORBS and was rejecting the callback based on the hosts listing in SORBS. The callback system could not detect the difference between no such user and any other type of error, so it rejected the message as a callback failure.
Note: also noted there are a number of mail servers in nz which don't accept bounces at all (even to valid users) :-( rfc-ignorant.com anyone?
FWIW every host that doesn't accept postmaster@ or abuse@ that I send mail to gets reported to rfc-ignorant.org, and that means all future mail from that host to the mail systems I manage is more likely to get classed as spam and therefore junked. Regards, Matthew _______________________________________________ NZNOG mailing list NZNOG(a)list.waikato.ac.nz http://list.waikato.ac.nz/mailman/listinfo/nznog
participants (3)
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Craig Whitmore -
Jeremy Strachan -
Matthew Sullivan