Since the emails that your users *are* getting, i.e. the command response saying "blah blah has been sent to you under separate cover" is administrative mail that would have the null MAIL FROM:, I don't think the problem in this case would be that msn.com is rejecting MAIL FROM:<>. I sent a GET CURRENT SCLISTS to the Sierra Club LISTSERV, and the file returned was 31K. Could it be that MSN has put a limit on the *size* of messages it accepts? Does this seem to happen only with larger messages? Are you able to send that file to the person complaining from your own address? Francoise