Yes, your iPhone can receive mail from an Exchange server via POP or IMAP provided they are turned on.
If you have already set up POP with the Blackberries you simply need to use the same settings you would have entered for your Service Books on your iPhone.
If you don't have IMAP enabled you can turn it on (instructions vary depending on your version) and then use the same settings.
For more info on enabling IMAP on Exchange check your documentation or TechNet: Exchange 2003 or Exchange 2007
Very easy! (Well, kinda like a magic trick... easy once you've seen it done...)
In Alpine, go to '(S)ettings', then 'Collection (L)ists', then (A)dd new, fill in the fields:
Nickname: MyGmail
Server: imap.gmail.com/ssl/NoValidate-Cert/user=youremail@gmail.com
Path:
View:
Of course, Nickname is your choice, Server needs your proper email address, leave Path & View empty, there are specialized uses for them, I haven't needed them.
CTRL-X to save
From the main menu, going to 'Folder (L)ist', then selecting your new collection, should cause Alpine to prompt you for your password. Entering that, you should see your gmail folder (label?!) structure. For gmail's purposes, 'folder' and 'label' are identical.
You MAY need to start Alpine with the '-passfile=xxxx' command line option to cause alpine to remember your passwords rather than typing it in each startup of Alpine, but I forget if you need it all the time or just the once to enable it. Try setting up the "collectionlist" first, see what happens, it's been so long since I've started from scratch with pine/alpine/realpine.
You may add as many "CollectionLists" as you like, I've got several other imap accounts listed, you can adjust the order to put more frequently used ones up top or whatever.
I seriously recommend walking through the entire list of 'config' options and using the '?' help function to learn what everything does.
Hope it helps.
Best Answer
From Configuring Alpine:
Alpine e-mail setup also has Alpine setup instructions, including how to set up Gmail using POP3 (including pictures):