IBM have announced that in release 8.0.1 of their Domino messaging and database server product, scheduled for early 2008, they will provide push email support for Windows Mobile devices:

Mobile support for Lotus Notes and Domino Web Access users through IBM Lotus Notes Traveler- Following the shipping of Lotus Notes and Domino 8 that began worldwide in August, IBM is announcing Lotus Notes Traveler, a new client for Lotus Notes and Domino 8.0.1.  Currently scheduled to be available in the first quarter of 2008,  Lotus Notes Traveler will provide out-of-the-box, mobile support for Lotus Notes and Domino Web Access users, enabling access to Lotus Domino mail from Microsoft Windows Mobile devices.  As currently planned, Lotus Notes Traveler will provide automatic, real-time replication of email, including attachments, calendar, address book, journal and to-do’s and will work over all wired and wireless connections.  

Read the full press article here:

http://www-03.ibm.com/press/us/en/pressrelease/22325.wss