We also just discovered once you change the MTU to 1280 on the UTM you can no longer connect to Office 365 Lync over a wireless connection. If you change the MTU back to 1500 on the UTM Lync connects without issue, but your wireless connection is basically unusable. The only way to get Lync to connect and have decent performance is to set the UTM to 1280 and force the MTU on your wireless card to 1280. This isn't really a solution. Sophos needs to get this fixed ASAP.
We also just discovered once you change the MTU to 1280 on the UTM you can no longer connect to Office 365 Lync over a wireless connection. If you change the MTU back to 1500 on the UTM Lync connects without issue, but your wireless connection is basically unusable. The only way to get Lync to connect and have decent performance is to set the UTM to 1280 and force the MTU on your wireless card to 1280. This isn't really a solution. Sophos needs to get this fixed ASAP.