I have seen quite a few strange error monitoring reports come from ListServ the last month or so. Below is one of them: Err First Last Address --- ----- ----- ------- 1 02/03 02/03 [log in to unmask] Last error: SMTP; 550 <[log in to unmask]>... User unknown This looks quite ordinary. However, I know for a fact that this person is not nor ever was on the list in question. The list is a closed, internal list. A few other list owners asked me about this same problem. Again, their lists were closed, internal, and confidential. For one day that I looked, I did notice that someone sending to one of these closed lists was put onto the monitoring list. I checked sendmail's logs, but there was no error message for the owner- alias, and the only mail passing through the ListServ machine from this person was to the list itself. Another strange user is Err First Last Address --- ----- ----- ------- 2 02/07 02/07 [log in to unmask] Last error: SMTP; 550 <[log in to unmask]>... User unknown Anyone seen this before? Any ideas? I can't tell if this is ListServ or the sendmail m4 definition for the type of machine, which is OSTYPE(aix4) These don't happen very frequently, maybe twice a month. Any help is appreciated. Thanks. Bob Jackiewicz UIC Academic Computer Center [log in to unmask] University of Illinois at Chicago Network Services