Hi @ll,
this is what happened today.
In my eaten mails log I found an email that was sent by a former schoolmate of mine who did not know my real email address. As he did not know it because I had never given the address to him, he must have tried to find it by using google.
He probably found several email adresses together with my real name, but I have not used these addresses for a while, changed my accounts, closed accounts etc., so he received the usual error message from all of these saying that the user or the account does not exist.
The SG that he found was for newsgroups, but after I received enough feedback via that address I set its counter to 0 so no new mail would come through. It was by accident that I looked at the website of SG and my eaten log today and noticed he tried to send me something and did not succeed.
Unfortunately, as SG never sends back any messages whether or not delivery was no success, my school mate now will assume the mail address was indeed correct, and because he did not receive any error messages he must assume now I do not want to respond and the mail itself arrived at where he sent it to.
This is one of the (perhaps rare) occasions where one would like to have some kind of response going back to the originator of an email saying something like "does not exist" or whatever.
Perhaps time to think of a switch for it?