ActiveSync is a pretty straight forward component to activate on IAG.... or at least it normally is, but I got an support question about it today.
Probably best to start with the basics first, and some more useful information gathered along the way.
The starting point with most application should be this document regarding applications that IAG is aware of: IAG Application Aware [1.0Mb]
Someone pointed me towards these Microsoft blog entries, which gives a little more detail:
Publishing Microsoft Activesync through IAG2007 - Part 1 of 2
Publishing Microsoft Activesync through IAG2007 - Part 2 of 2
Another useful component is this Microsoft Exchange Server Remote Connectivity Analyser, which can test the connections to ensure your configuration works. (Thanks Andrew for showing me this, it will be very useful!)
The analyser will allow you to check the connection including SSL certificates and server name, connection to the trunk, AD authentication, connection to the Exchange server and the OPTIONS commands.
The issues we had today were regarding the OPTIONS commands, as everything else seems to work. More investigation to follow..... and hopefully an answer!