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Why are members of my mailing list being unsubscribed without my authorisation?

Mailman uses a bounce-processing procedure so as to suspend, and later remove, subscribed addresses from mailing lists if email to them cannot be delivered.

Essentially, if an address bounces (that is, email is returned from it as undeliverable), Mailman makes a note of the bouncing address and the severity of the problem that caused the bounce.   If the address continues to bounce and the underlying problem is severe enough, Mailman suspends the address in the mailing list so that it is no longer sent emails, but it sends reminders to that address at intervals to try to inform the subscriber of the problem.   If the reminders continue to bounce, after a certain time the address will be completely removed, automatically, from the list.

List administrators can find full details of this mechanism in the Bounce processing section of their mailing list's admin page.

Similar problems can arise if a subscribed address is forwarding its email to another address.  For example, suppose a Sussex subscriber, Ann Other, is subscribed to a mailing with the email address, but Ann's Sussex account is forwarding all its email to an external address,  If a problem arises such that the external address rejects email, the rejected (bounced) email will be treated as arising from the subscribed address ( and it would be that address that would be suspended, and later removed from the mailing list if the cause of the bounces is not resolved.

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This is question number 2523, which appears in the following categories:

    Created by Andy Clews on 9 November 2012 and last updated by Richard Byrom-Colburn on 20 October 2016