I was using Paul Gregg's checkpoppasswd.c to authenticate POP3 users with a single-system-user id. The program used a linear search to find a user; this could become inefficient when the user base is large. Also, it could not resolve two different users at different domains using the same login name like the case "[EMAIL PROTECTED]" and " [EMAIL PROTECTED]". I made some simple modifications to the program so that a PostgreSQL database ( which supposedly uses a B-tree to perform a search ) is used to do the authentication; search based on the username and the full hostname is performed. Interested users can obtain the source code of the program at http://www.csusb.net/free/qmail/checkpass.c.gz Regards, Tong