I will chime in and add my US$0.02.  I'm very happy with the AOL error
message scheme--it's readable and it makes sense.  Either a user is not
known or the user's mailbox is full.  None of this potentially-confusing
"Cannot write to [USER.MAIL]MAIL.MAI" or "Unknown Mailer Error 1" or
"Disk extend failed writing to blah de blah de blah."  And yes, you can
set a full mailbox user to nomail and delete an unknown user.
 
David, Eric should be able to send you the info on the LISTSERV/LMail
autodelete formatting if he hasn't already.  I'm sure many list owners
would shout "Halleluyah!" if a major Internet player was formatting
its error messages in such a way...:)
 
Nathan