North American Network Operators Group

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Re: incorrect spam setups cause spool messes on forwarders

  • From: Randy Bush
  • Date: Mon Dec 01 13:55:44 2003

>> is the following a general problem, or just one i am seeing?
> Verizon does SMTP callbacks, connecting back to the MX of the envelope 
> sender and trying to verify that the user exists
>> 2003-12-01 10:09:05 1APbBa-000Ork-DY == [email protected] <[email protected]> R=lookuphost T=remote_smtp defer (0): SMTP error from remote mailer after MAIL FROM:<[email protected]> SIZE=5365: host []: 450 Requested mail action not taken-Try
> So this would connect to the MX of and try to verify 
> that [email protected] exists.
>        5h55m6s IN MX   0
> If the MX ( doesn't respond fast enough for 
> verizon, their tester times out, and the message gets 4xx'd.

interesting but utterly irrelevant.  the question was not how
verison decided it was spam.  the point was that their server
returned a 450 as opposed to a 5xx (550 looks good), and this
causes net damage.