SBS 2000 and Iphone (which is best way to check mail.)

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I know this news group doesn't get much activity, so any help would be greatly appreciated!
I am managing a sbs2000 server on a low budget (no budget). How can I best check email from the Iphone?

The way I understand it I have a bunch of options:

owa - not sure if supported well on sbs2000
pop - the user's mail box is about 1 gig, will this be a problem?
imap - what would I have to do for this?
other's - will any others work with sbs2000?


Thanks so much!
Joe.

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