>        Hello all.  Sorry by the extension of this mails, but I think 
>that log is necesary.
>
>        Some times, when listserv is sending a mail, some real users 
>appear as User Unknow. For example, in this case, when send a mail 
>to a users-uam-l list  (about 2900 subscribers), listserv dosn´t 
>identify some users, and this users are in aliases. Always  happen 
>whith  consecutive users.
>
>        Aliases  and the list  are sorted alphabetically, an in this 
>case, listserv "lost":
>
>[log in to unmask]
>[log in to unmask]
>[log in to unmask]
>[log in to unmask]
>[log in to unmask]
>[log in to unmask]
>.... (more users)
>
>Some idea??. It´s a listserv problem??.  This users never lost 
>particular (single) mails

This:

>May 12 13:19:28 naranjo sendmail[1367]: NAA01328: 
>to=<[log in to unmask]>, delay=00:00:12, mailer=local, stat=User 
>unknown   *****************>>>>>>>>!!!!!!!!  Lost user

indicates to me that it is sendmail that's trying to make the 
delivery and is getting back a "user unknown" response (and hence 
it's not a problem with LISTSERV).  Since it's happening to 
consecutive users this indicates a temporary problem which clears up 
by itself quickly.  If this only happens for users in a particular 
domain then I would suspect an intermittant problem with their mail 
server; if not then perhaps there's a problem with the sendmail 
installation whose log files you quote above.

This discussion is probably more appropriate for LSTSRV-L (which is 
for LISTSERV site managers).

Thanks,
-- 
Jacob Haller, Technical Support
L-Soft international, Inc
http://www.lsoft.com/