[Mailman-Users] Un-subscribe notification

[Tonya Robison]

Hey, 
I received an email from mailman-bounces at mydomain.com notifying me that a
member has been unsubscribed. This person has not requested to be removed
nor was notified to be removed. This happened about 3 weeks ago but with
about 10 members in one day. How do I keep my members from being randomly
removed? Thanks for your help!
Tonya