[MM3-users] Moderation request email from a non existing user

Every day mailman (MM 3.3.3 (Tom Sawyer)) sends me an email with a held unsubcription request from X user. This user is not subcribed to that list anymore but every day an email is sending to the list owner. On the web interface there's nothing pending for approval or similar. Is there anyway to avoid receiving this anoyning email every day? Thanks in advance.

David