When you first subscribed to the list, the server sent a message to the email address you signed up with, to ensure that it was indeed you that requested membership. More accurately, to ensure that the person receiving email at that address had indeed requested to add that address to the mailing list. In the same way, if you unsubscribe from the list, a message will be sent to that address to ensure that you (the person recieving mail at the to-be-unsubscribed address) actually requested that address to be unsubscribed. This is so that if someone spoofs an unsubscribe request that looks like it came from your address, the server still sends a message to that address (you) requesting verification before unsubscribing you. It prevents random strangers from being able to unsubscribe you. So if you ever get a message from the list server asking for verification that you requested to unsubscribe from the list, but you never requested to unsubscribe, just ignore that verification message. No one other than you will ever request that you be unsubscribed.