[Mailman-Users] Bounces threshold never reached

Mark Sapiro mark at msapiro.net
Tue Jun 7 03:42:08 EDT 2016

On 06/07/2016 12:19 AM, Kala Balik wrote:
> It seems that my real misunderstanding is even more fundamental. I was
> expecting Mailman to retry sending an email if it received a bounce for
> that adress. I thought it would retry until either no new bounce was
> received anymore or the bounces threshold was reached. But this really
> is a misunderstanding, right? Mailman does not retry sending emails, right?

Basically 3 things can happen to a message sent by Mailman.

1) The outgoing MTA responds with a 5xx permanent failure. In this case,
Mailman records that as a bounce and that's the end of processing that
message for that recipient.

2) The outgoing MTA responds with a 4xx temporary failure. In this case,
Mailman puts the message in its retry queue and retries it periodically
(defaults every 15 minutes for 5 days). If it is ultimately sent, fine,
otherwise Mailman eventually gives up and treats it the same as a 5xx.
This will increment the bounce score by 1 after 5 days.

3) The outgoing MTA is able to deliver the message to the recipient's
mail exchange server. It is possible that the recipient MX will accept
the message but later it or some other MTA in the delivery chain may
return a non-delivery DSN to the listname-bounces envelope sender.
Mailman receives this DSN and attempts to recognize it (it's pretty good
at this), and if it is recognized as a failure, Mailman records a bounce
for the recipient. If it is recognized as a delay or other non-failure,
Mailman ignores it, and if it is unrecognized, it is forwarded to the
list owner if the setting for that is Yes.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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