Many , if not all, of us are getting a message that says something to the effect that <one or more of the addresses in your  messages has failed.> 
Not to worry - this is a former subscriber who has a full mail box and who we can't unsubscribe from this end.
Is an irritant rather than a major problem. Just work around it, ignore it and don't let your mailboxes fill up when you go on vacation.:)
Bill Evans for NYHIST-L