Will the webmail client being created work only with JBoss Mail Server or should it be able to work with any IMAP server?
We have a fairly extensive postfix + courier IMAP system that we might someday migrate to JBoss Mail Server (we do a lot in java right now). Our webmail is squirellmail and that is something I would migrate sooner.
The webmail does not use IMAP and is JBMS specific. There are several technical reasons for this (including calendaring, addressing, etc). Java is mostly a means to an ends for JBMS.