Ken's Blog | Windows Mobile 5.0's "Push E-Mail" is really "poll" email?!?

Friday, 10. June 2005

Windows Mobile 5.0's "Push E-Mail" is really "poll" email?!?06/10/2005 05:40 PM

So I was all impressed with Windows Mobile 5.0 finally supporting "Push E-Mail". It turns out that it's really a variation on polling! Whoops. MS Marketing does the rename-er-ooo again. Dang, I wish I could sell stuff like they do

From a link on Brighthand, there's a MS Exchange Team blog that covers the internals of how this works. Well, at least now we know why MS hasn't tried to submit this as a "standard". It requires hacking up your mail server's HTTP stack (assuming it has web mail support).

This is roughly how RIM/Blackberry's push email works: each device has something similiar to a network MAC address. When it registers with the global BES server (sitting in some NOC that your cellular provider runs) which lets BB's server (on your site) talk to the device. The device is always listening on a port for messages from the BES server. All communication is encrypted and devices are "tied" to users, which is why corporate types like it. It's basically a variation of Dynamic DNS, which is also why devices used to get "untied" in BES 3.x (supposedly fixed in BES 4.x).

MS' solution is basically doing HTTP GETs from the server and taking advantage of how HTTP timeouts work. The device fires up a thread that polls a web page on the server and the thread waits for a response. If the server sees any new stuff, it returns a message that the device interprets as "fire up ActiveSync to grab some email". If there's no work yet, the server doesn't return a response until some timeout has been reached (though I'm not sure why the server needs to worry about timeouts at all since the device's thread can handle the timeout). Because it doesn't have to periodic ActiveSyncs, it's less network intensive than the current MS AUTD solution.

While it's laudable that MS wants to avoid any sort of BES equivalent, it's very MS-Exchange-centric. It's purely tied to email (you have to specify folders to poll; what about other apps? Guess no one running Exchange uses custom apps like Lotus Notes users do

and MS Exchange 2003 (which most people aren't even on yet because of the huge migration hassles of Active Directory

. On the bright side, it's probably fairly trivial to reverse engineer this (though it'd be nice if MS would just document it for us for once!) to work w/ other email servers, assuming the device's polling URL can be configured; even if not, you can probably work around it by adding an appropriate URL mapping. I'd just need a short session with a network analyzer and someone has to donate an MDA IV/UTC Universal to me for a few years to get this to work

Update: there is a MS Webcast which details how it works w/ Exchange

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