Been getting to the bottom of how the service pack 2 and the feature pack for Exchange 2003 will work with Windows Mobile 5.0 devices, particularly the way the new “push” e-mail works.
Firstly, let me state my understanding of what true “push” e-mail is.
- User experience: As an e-mail is delivered to the user’s Exchange mailbox residing on a server, a server side trigger sends the e-mail directly to the user’s remote device. For the user, mail comes in to their device in real-time, not in scheduled chunks.
- Security: The E-mail is pushed to a trusted device from a server residing in the perimeter network. The device does not initiate this connection. This means no external firewall port for incoming device connections is required. This is the security model that has contributed to blackberrys’ success.
Ok, so what push functionality does WM 5.0 and Exchange SP2 have? As per my definitions above, it only delivers the user experience.
The short of it is, everything is still “pull”. That is, the device initiates almost everything. The new addition is that notifications to the device to begin a pull are now IP based, rather than the messy and expensive SMS approach.
How it works:
- The WM 5.0 device registers to a GPRS data network.
- Activesync (if configured) on the device then connects to the exchange server.
- This connection state is maintained, controlled by the session disconnect interval on your firewall. If the device loses connection, or the firewall drops it, it will re-connect again.
- The WM 5.0 device lets the exchange server know it’s network IP. It will update the server if this changes.
- The Front End Exchange server, monitoring the back end mailboxes for changes, fires off a notification to this IP if a new e-mail comes in.
- The device receives the notification, and then begins an E-mail pull.
All data traffic between device and server is XML through HTTPS (with SSL). GZIP is used to compress the data to keep data usage to a minimum.
What does this mean? On the good side, a better user experience, less data sent and recieved overall through GZIP. I also noticed the first initial sync is a lot faster. The new WM 5.0 interface looks great too, and with viewing for powerpoint, word and excel files built in, it is more useful out of the box for attachments. (Although smartphone viewing an attachment isn't so hot) Apparently better battery life…according to the Microsoft chaps, although I’m still not sure how true this is.
On the down side, the pull still means that you can’t compare WM5.0 and Exchange SP2 apples for apples with blackberry, as the Blackberry still has a better security model. This is the biggest issue for me when trying to put mobile devices into the enterprise, far more a hurdle than up to date e-mail was.
Neil Chapman