iPhone/iPad sync with Zimbra accounts
The iPhone/iPad works really well with Zimbra NE.
When you get your iPhone/iPad, choose 'Exchange' as the type of account on the iPhone.
In the control panel on the iPhone you can enable sync for the calendar, and the calendar sync is immediate and if you set reminders for appointments they'll pop up on the iphone.
In the iPhone setup control panel, specify the Zimbra calendar as your default calendar - if you don't you'll run the risk of entering new appointments on the phone and have them not get into Zimbra.
To test whether you've got this set correctly, just create an appointment on the phone and then check your calendar in Zimbra to make sure the event has appeared there (it should appear immediately).
The email sync is great - it uses 'push' so you'll be notified as soon as new messages arrive.
Same goes for the iPad if you find yourself tempted to get one of those - just set up the account as an 'Exchange' account and you can handle your email and calendar there as well.