Certified Procedure for Unsubscribing From a Mailing List

I recently had the following problem: I wanted to remove from a mailing list I previously subscribed to but using the unsubscribe link they provided ended up to be useless. It seemed to work but in the end I kept receiving their emails.
I never thought of writing them to be removed since in my experience it's a total waste of time.
The good news is there are other solutions!
These services always offer you the possibility to update your personal info and included with that you can change your email address. I mean, they cannot loose a "valued customer" if he decides to change his email so that update link will work!
Given that, what you can do is use one of those incredible services like Mailinator to have a one time email you can put as your new email address. Of course you will be able to answer to their confirmation request by reading the only email you will get at that address, and after that forget about the whole thing!