|These policies control the automatic bounce processing system
in Mailman. Here's an overview of how it works.
When a bounce is received, Mailman tries to extract two pieces
of information from the message: the address of the member the
message was intended for, and the severity of the problem causing
the bounce. The severity can be either hard or
soft meaning either a fatal error occurred, or a
transient error occurred. When in doubt, a hard severity is used.
If no member address can be extracted from the bounce, then the
bounce is usually discarded. Otherwise, each member is assigned a
bounce score and every time we encounter a bounce from
this member we increment the score. Hard bounces increment by 1
while soft bounces increment by 0.5. We only increment the bounce
score once per day, so even if we receive ten hard bounces from a
member per day, their score will increase by only 1 for that day.
When a member's bounce score is greater than the
threshold, the subscription is disabled. Once disabled, the
member will not receive any postings from the list until their
membership is explicitly re-enabled (either by the list
administrator or the user). However, they will receive occasional
reminders that their membership has been disabled, and these
reminders will include information about how to re-enable their
You can control both the
of reminders the member will receive and the
frequency with which these reminders are sent.
There is one other important configuration variable; after a
certain period of time -- during which no bounces from the member
are received -- the bounce information is
stale and discarded. Thus by adjusting this value, and the
score threshold, you can control how quickly bouncing members are
disabled. You should tune both of these to the frequency and
traffic volume of your list.