As long as you can find out the name of the server you are on, it should be able to figure out many of the settings for you. Keep in mind that you will need to enter your name ExActLy as it appears in Active Directory - caps count on the iPhone. Certain syncing things don't work right if you don't put the caps in correctly (you'll have issues with meeting invitations).
For instance, I'm on a server called Redmond. My username is:
Redmond\Sinecure
My "description" is
[email protected]
SSL is On. Email is
[email protected] (don't bother trying that - I'm making up the "ourdomain" part). Server is mail.ourdomain.com
Keep in mind that once you set it up successfully, its going to ask you if you want it to overwrite your calendar and contacts on the phone. If you are currently syncing to MobileMe for something personal, those will be wiped out on the phone. Its a one or the other deal, you can't have Exchange calendar/contacts plus non-exchange ones.
Also, one surprise for me when I set it up was that it asked me for a passcode instantly upon successful set up. I mistakenly thought it was asking once again for my Exchange password so I entered that (its long and complex). Ooops. What it was asking for was a turn-on passcode for the device, which only needs to be 4 characters and I like to keep it simple so it doesn't take me too long to turn on the phone.
Hope that helps.
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