Question : linux postfix mail server

Dear All

I am having rhel5 working as mail server with postfix , dovecot imap but this uses /etc/passwd for the mail user authentication as i have around 80 real users but only 20 users are required to use the mail service , remaining 60 users from the internet should be able to use only ftp service they should not be able to use the mail service , i think one method is making mysql authentication for this i have to uninstall the postfix rpm and install the source with feature of mysql.  can anybody help me any other method so that only 20 users can use the mail service , thanks in advance.

Answer : linux postfix mail server

I think setting up an LDAP server for authentication would be the best way to go. Either switch the internet users to LDAP and integrate that with the FTP server or switch the Postfix authentication to LDAP and leave the other users as local. Whichever is easier.