Microsoft Exchange Server 2003 includes various products and services that support mobile computing. These offerings dovetail nicely with the hierarchy of clients, from most to least functional.
- Microsoft Outlook offers the most functionality but has the greatest resource requirements. It's also the least portable of the Exchange mobile products, both in terms of the machines it runs on and the fact that it requires Windows and doesn't run on other OSs.
- Exchange ActiveSync is a service that lets you synchronize email, calendar, and contacts with Pocket PC and Windows Powered Smartphone devices.
- Outlook Web Access (OWA) offers much of Outlook's functionality; however, you must access it through Microsoft Internet Explorer (IE) or another browser. OWA requires a fairly high-resolution screen, making it unsuitable for most mobile devices. (Some portable devices can successfully render OWA pages, but they tend to look bad when squeezed below the 800 × 600 minimum resolution that Microsoft recommends.) For most users, the biggest drawback to OWA is that it offers no offline access.
- The familiar POP and IMAP services offer message access to essentially any device that can display text and send TCP/IP packets. Most of the current crop of PDA/phone devices (such as the Sony Ericsson P800, Kyocera 7135, and Samsung i600) can do either or both. However, compared with full Outlook, neither of these protocols is feature rich. In particular, POP has no concept of folders, and most IMAP clients don't adequately support the folder set that Outlook uses.
- Outlook Mobile Access (OMA) is a data-browse feature that lets compatible devices access messages in the Exchange Inbox, Calendar, and Tasks folders.