ActiveSync with wifi and 3g

[Guest helfire]

been setting up push email and active sync. Everything works great when using 3g or an external wifi conection. But as soon as i conect it to my lan with USB or wifi the sync fails. My set up is home sbs server and a isa 2006 firewall server.

In the server setting for active sync i put on my external outlook web access i.e. owa.mydomain.com and this works great. But when i conect to home lan via wifi it fails. Now ive tried pinging owa.mydomain.com and it resolves the ip address to my sbs server (got a spit dns setup). Is anyone else having any isues with this.?

Chris