Currently, those who click on "unsubscribe" get a pop up message that reads "Please remove me from your mailing list.  (email address) will no longer receive emails from the (sender)."

This statement is confusing - are unsubscribers removing themselves from a mailing list or an email list?

A very simple solution is to reword the statement to read, "Please remove me from your email list.  (email address) will no longer receive emails from the (sender)."