Is there an easier way to control which users have IMAP access though a GWIA
than by editing the class of service?

What would be nice is have a eDir group which would define the users that
can have access.

By default I have it set class of service that enables IMAP access for
everyone however I finding that more users are passing along the server
addresses and adding their mobile device to send/retrieve email which is
working but I would prefer some control over who and who doesn't have access
without cutting everyone off and adding them to the properties of the GWIA