The manual is specific: Exchange email can only be used in IMAP mode. Nothing in the manual gives any indication that the iPhone supports ActiveSync at this time.
I do know that there was mention that Yahoo! mail was supporting "push IMAP," though I assume this is just IDLE command, and if so, I can't see why other IMAP servers using this standard wouldn't work...
Shame about the lack of ActiveSync. How about a native iPhone zimbra client? Pretty please? | 
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