[imp] Recommendations on what components to use / how to configure my system?

[Chad Day]

A little background on what I am trying to do:

I am setting up a site to host a bunch of domains for hockey teams I play
on.  I want to offer them all webmail with one IMP installation.   I don't
want to give shell logins to everyone, obviously.  I want players on each
team to be able to go to http://mail.theirteamname.com and login with their
username/password, and I don't want them to be able to log into other teams
sites (saw this on the horde FAQ about virtual hosting and stuff).  There is
also the complication that I may have 2 jsmiths, 1 on 1 team, 1 on another,
so I'm not sure how best to tackle that situation.  I don't know anything
about LDAP, but I was thinking about picking up a book today to start
learning about it.  I have other applications I want to tie in (forums and
stuff) that are written in PHP and use a MySQL back-end, and I want to have
one login/password for the entire site, so I would definetly want to store
the user info in MySQL.  If I do that, is there even a need for LDAP?

Can anyone point me in the right direction?  I basically just need help
deciding on a starting point/framework, and then I can start setting it
up/researching those aspects ..  so any help is greatly appreciated here.
Thanks!

Chad