Exchange ActiveSync Direct Push

[Maxim]

Hi!
I'm having an issue with Exchange ActiveSync: there are following events periodically logged in Application Log:

Event Type:	Warning
Event Source:	MSExchange ActiveSync
Event Category:	Requests 
Event ID:	1040
Date:		27.07.2011
Time:		8:49:26
User:		N/A
Computer:	ELECONEX02

Description:
The average of the most recent [525] heartbeat intervals used by clients is less than or equal to [540].
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.

However, the article at Microsoft's Technet describes the solution only for ISA Server. Maybe someone knows how to deal with this situation using IPF?

Thanks!