[Mailman-Users] Rejected or bounced messages.

Barry S. Finkel bsfinkel at att.net
Wed Jan 1 23:47:45 CET 2014

On 1/1/2014 4:33 PM, Joseph Brennan wrote:
> These three were stopped after RCPT, so the problem is not about
> content. Most likely the recipient address is not deliverable.
> <mail at me.com>: host mx6.me.com.akadns.net[] said: 550
>    5.1.1 unknown or illegal alias: username at me.com (in reply to RCPT
>    TO command)
> <mail at cgocable.ca>: host mx2.cgocable.ca[] said: 550 #5.1.0
>    Address rejected. (in reply to RCPT TO command)
> <mail at msn.com>: host mx2.hotmail.com[] said: 550 Requested
>    action not taken: mailbox unavailable (in reply to RCPT TO command)
> The first one is the unusual case.
> <mail at epdot.com>: host mx1.megamailservers.com[] said: 550
>    5.7.1 s01D0qcI004613 This message does not comply with required
> standards.
>    (in reply to end of DATA command)
> I've never seen this error before.
> Google "This message does not comply with required standards" to find a
> lot of people speculating about what it means, going back to 2006. They
> all relate it to Exchange or Outlook, but mx1.megamailservers.com says
> it is running Sendmail 8.13.6, and this is not a standard sendmail error
> message. So it's a custom filter on megamailservers.com.
> Here's an example involving Mailman and megamailservers.com from 2007!
> <http://list.web.net/archives/getsmart-l/2007-December/002525.html>
> ... with complete message attached. I don't see anything wrong with it.
> Joseph Brennan
> Columbia University IT
> ------------------------------------------------------

I did a Google search, and it appears that the destination mailer
found something objectionable with the mail (maybe a URL that
it did not trust, or the mail was to be flagged as spam),
so the destination mailer terminated the SMTP session
with a fatal 5.7.1 error message.  Most of the sites I saw
were, as Joseph noted, from Outlook or Exchange users who were
trying to blame MS, when it was the sending MS mailer that was
reporting what the destination mailer reported during the SMTP
dialog.  There must be some anti-spam/malware software running
on the destination mailer that is treating something in the mail
as objectionable.  If I remember the SMTP standard correctly,
mail can be rejected during the DATA phase of the dialog.

In the other three examples, the sender sent the SMTP command

      RCPT TO:<user at example.com>

and the destination mailer rejected the mail at that point because
the mailbox did not exist.  It is always better to reject a mail
message during the SMTP dialog because, once the mail has been
received, it is harder to reject the mail and notify the sending

--Barry Finkel

More information about the Mailman-Users mailing list