Recently we have had reports of users not being able to send or sync emails to / from Apple iOS devices. When we look at the ActiveSync logs, we see the affected people getting HTTP 503 errors. Yet if this person works on a Windows Mobile device or an android Mobile device - they do not have the problem. Similarly, if the person uses the new "Outlook" app on an Apple iOS device, they don't have the problem. It only occurs with the native mail app on iOS devices.

We have Exchange 2013 CU5 - 4 x CAS Servers on Windows 2012, and 6 x Mailbox servers on Windows Server 2008 R2 (hardware doesn't support WS2012).

We have logged a call with MS Support and they are looking into it, but was just wondering whether anyone else has seen this issue.

PS - Before anyone suggests it - we have new servers on the way for the mailbox servers, and will install WS2012R2 and CU8 on it when they arrive.  But because our executive is being affected now, we need to look at this now.