CentOS 5 Server :: Adding Authentication Modules To Courier-imap?

I am administrating a server with CentOS installed. It came with qmail and courier-imap preinstalled, and Plesk.I need to manually add email accounts outside of Plesk, because my 1-domain Plesk license only allows the creation of one email address (yes, it sucks).

When I say add email account I mean creating a new email address, have email for that address be stored in its maildir, and have a corresponding imap (and hipefully also pop3) account that will be able to read that mail. All this with virtual domains.I've already found out how to create the new email addresses for qmail, so that email for the new email address is being delivered correctly. Now I need to create the imap/pop3 accounts for courier.

For the qmail part, I create a folder in in /var/qmail/mailnames/virtualdomain.org/username and a maildir called Maildir inside it. This is how the first mail address was created by Plesk and i'd like to maintain the same structure. As I've said, the qmail part is already working, I need to get the courier-imap part to work. Ideally, it should accept login with both short (i.e. myuser) and long (i.e. myuser@virtualdomain.org) user names.

Currently the only authentication module that is enabled in courier-imap is authpsa, which is Plesk's authentication module.in order to add more authentication modules, do I just need to add them to the authentication module list in /etc/courierimap/imapd, or do I need to reinstall courier-imap with support for such authentication modules? I thought I would only need to add them to the list, but I've noticed that the /usr/lib/courier-imap/authlib/ folder only contains a binary called "authpsa". Does that mean that other authentication modules are not even installed? If so, can I install them without reinstalling courier?

The second question is, what would be the most recommended authentication module that would make it easiest to create new email addresses/accounts from the command line? I need to be able to write a shell scripts capable of creating a new email address with all that is needed, and I'd like to keep this script as simple as possible, so for example I'd avoid mysql-based authentication as it sounds rather complicated. And the last question is, if I do need to reinstall courier-imap, how can I install a package without recompiling it? Will my one existing mailbox keep working?