Exchange 2010 OWA Hangs

This is not going to break anything for ActiveSync. Accept-encoding header only controls whether the client accepts compression and what type of compression. Since LTM is a full proxy, it is typically tasked with compressing content to the client if the client sends Accept-Encoding header(all modern browsers do). However, sometimes CAS servers are also configured to do compression, and that is unnecessary burden on the server, so unchecking Keep Accept-Encoding simply removes that header from the payload before it reaches the server and stops the server from compressing content. Hope it makes sense.