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[address@concealed]

Hello,
How do you solve such problem:
everybody can unsubscribe someone from some lists if knows her(his) email
address and list. How to stop or prevent this. 
This is to say that if I'm subscribed to list ngo and my email address is
address@concealed, evryone can send a message to address@concealed with command
"unsubscribe address@concealed ..." and I'll be removed from list.
Please mail me existing solutions.
Thanks.

        Eugen