I suspect that the recipient has had mail forwarded to the second address.
You have to guess who g\has a similar name or address.
 
At 10:54 AM 9/15/96 +0200, you wrote:
>Hi.
>I have a strange problem. The listserver bounces mails to the list to me.
>That is, all mails to a certain person who isn=B4t even ON the list.
>Therefore I can't delete him, or sett him on NOMAIL. So I keep getting all
>these bounces. I have also tried to mail to the adress privately, but that
>bounces too, just like when I try to mail to the postmaster. Do you have
>any idea? (The erorreport follows.)
>
>>One or more addresses in your message have failed with the following
>>responses from the mail transport system:
>
>>   User <[log in to unmask]> not known at this site.
>
>>Should you need assistance, please mail [log in to unmask]
>
>>-------------------- Returned message follows ---------------------
>
>Cecilia von Melen
>=46reelancewriter
>Tel & Fax: 46-8-540 643 77
>[log in to unmask]
>
--
Craig Gjerde, Ph.D.  [log in to unmask]  University of Wisconsin
                      Co-listowner for Family-L