The issue is also documented by Brian Reid: Exchange Web Services (EWS) and 501 Error and Phil Sharp: Kemp Load Balancer and Lync Unified Contact Store Integration Note.Īfter enabling L7 debug tracing on my KEMP LoadMaster I observed the same error mentioned in the above articles “lb100 kernel: L7: badrequest-client_read (-501):
Microsoft provides great testing tools for Exchange on so I decided to run EWS connectivity test from the toolset. What I didn’t know at that point is which element in the HTTP request was causing the server to reject the request. The error is somewhat misleading as when you look at EWS logs on Exchange server, you see that the server rejected the request with HTTP error 400 which translated to “bad request”. Mac Mail would show “Account Error” which read “Unable to connect … The server returned error: Connections to host on default ports failed.”
It is worth pointing out that while Outlook 2013/2016 on PC use MAPI/HTTP or RPC/HTTP to connect to Exchange 2013/2016 servers, both clients on Mac (Mac‘s own Mail client and Microsoft Outlook for Mac) use EWS to connect.
#MAC MAIL SERVER ERROR FOR MAC#
Latest Microsoft Outlook for Mac did not exhibit any issues either! Microsoft Outlook 2013/2016 clients on PC did not exhibit any issues.