It's running windows mobile, so all the usual stuff. EAS, windows live push.
Problem with EAS is you need an exchange server in order to utilize it. There used to be some free ones like Mobipush, but Mobipush is dead now.
Generally speaking it's not as elegant as blackberry imo, but you don't have some of the limitations that come with BIS (like download attachment limits).
I think as of WM 6.1 imap idle is still not supported as standard...
