Ports to forward for Exchange?

I've got a client that wants us to poke holes in the wireless DMZ->internal so that their users on the wireless can get mail with Outlook and phones - do I need to open up any ports besides 25 for this? Obviously I'd like to minimize the open ports available, but it seems like there are several used (80 and 443 also seem important for some Outlook functions like autodiscover and OAB).