Exchange SP2 ActiveSync Direct Push and firewall HTTP connection timeouts

"Exchange SP2 ActiveSync Direct Push and firewall HTTP connection timeouts" Boy, does that sound like an exciting title to a blog entry or what?! And I wonder why I have not gotten the Blog Pulitzer yet. :-)

If you have installed Exchange 2003 SP2 and have been lucky enough to get a Windows Mobile 2005 FP1 update for your mobile device (from your device manufacturer, not Microsoft), then you may have been playing with the Direct Push feature. (This lets Exchange notify your device via a pre-established, pesistent HTTP or HTTPS connection that you have new mail to download.) However, if your firewall's HTTP timeout is set to less than about 8 minutes, the devices may not keep their persistent connection open. You will see errors such as this:

Event Type: Warning
Event Source: Server ActiveSync
Event Category: None
Event ID: 3033
Computer:HNLEX01
Description:The average of the most recent [200] heartbeat intervals used by clients is less than or equal to [9]. Make sure that your firewall configuration is set to work correctly with Exchange ActiveSync and direct push technology. Specifically, make sure that your firewall is configured so that requests to Exchange ActiveSync do not expire before they have the opportunity to be processed. For more information about how to configure firewall settings when using Exchange ActiveSync, see Microsoft Knowledge Base article 905013, "Enterprise Firewall Configuration for Exchange ActiveSync Direct Push Technology"

Microsoft recommends that the HTTP or HTTPS connection timeout value on your organization's firewall be set to no less than 30 minutes. The heartbeat value on the Exchange server can also be tweaked with the MinHeartbeatInterval and MaxHeartbeatInterval registry values defined in KB 905013.