My system is a SLES11 sp4 server with 2xXEN VMs for GW2014 & GW Mobility server respectively.

Everything has worked as expected for 18 months. Recently however, I noticed that while new incoming mail is reported and viewable on my mobile phone & iPad, the GW client on my Windows 10 is not automatically showing new mail. If I click send/receive they arrive.

I'm not aware of having changed any settings. What could be causing this?