|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 bounce
score 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 membership.
You can control both the number
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 considered 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.