MIT Mailman User Guide:
Bounce Processing

MIT Mailman

Many list owners have seen bounces to email sent to a list, often seen as a return from "mailer daemon" when email didn't get delivered. Mailman can be set up to intercept bounces and try to automatically process them. In addition, list owners can customize what happend when too many bounces occur.

These are the options available on the Bounce Processing Screen:

Bounce processing

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.

Bounce detection sensitivity
Should Mailman perform automatic bounce processing?
(Details for bounce_processing)
No Yes
The maximum member bounce score before the member's subscription is disabled. This value can be a floating point number.
(Edit bounce_score_threshold)
The number of days after which a member's bounce information is discarded, if no new bounces have been received in the interim. This value must be an integer.
(Edit bounce_info_stale_after)
How many Your Membership Is Disabled warnings a disabled member should get before their address is removed from the mailing list. Set to 0 to immediately remove an address from the list once their bounce score exceeds the threshold. This value must be an integer.
(Edit bounce_you_are_disabled_warnings)
The number of days between sending the Your Membership Is Disabled warnings. This value must be an integer.
(Edit bounce_you_are_disabled_warnings_interval)
Should Mailman send you, the list owner, any bounce messages that failed to be detected by the bounce processor? Yes is recommended.
(Details for bounce_unrecognized_goes_to_list_owner)
No Yes
Should Mailman notify you, the list owner, when bounces cause a member's subscription to be disabled?
(Details for bounce_notify_owner_on_disable)
No Yes
Should Mailman notify you, the list owner, when bounces cause a member to be unsubscribed?
(Details for bounce_notify_owner_on_removal)
No Yes

MIT Updated April 28, 2003. Copyright © 2003 Massachusetts Institute of Technology
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