Setup
Exchange 2013 CU10
Two servers with DAG
HA Proxy with Public IP Addresses and NAT
Exchange servers and AD with Private IP range 192.168...
Autodiscover is setup using the HTTP redirect method and testing just Autodiscover succeeds
Outlook Clients 2013 and 2016 work perfectly however when run the Outlook connectivity test I get the following failure:
Testing MAPI over HTTP connectivity to server mail.publicdomain.com
MAPI over HTTP connectivity failed.
Additional Details
Elapsed Time: 123 ms.
Test Steps
Attempting to resolve the host name ex02.internaldomain.lan in DNS.
The host name couldn't be resolved.
Tell me more about this issue and how to resolve it
Additional Details
Host ex02.internaldomain.lan couldn't be resolved in DNS InfoDomainNonexistent.
Elapsed Time: 123 ms.
What I don't understand is where is the DNS trying to resolve that from, is it trying to resolve that internal name from outside the network, then I'd expect that to fail, although I could have sworn that I got no failures the first few times I ran this test. MAPI has been configured and both internal and external url's are configured to the public address mail.publicdomain.com, Outlook connects fine and is functioning, for both 2013 and 2016, although I upgrade my machine from 2013 to 2016, so can't tell you the exact version number if that makes a difference.
Running Test-OutlookConnectivity -RunFromServerId EX01 -ProbeIdentity OutlookMapiHttpSelfTestProbe and Test-OutlookConnectivity -RunFromServerId EX02 -ProbeIdentity OutlookMapiHttpSelfTestProbe from both servers also succeeds.
The connection status within Outlook shows the protocol is HTTP with server name values of https://mail.publicdomain.com/mapi/emsmdb/?MailboxId=someguid@domain.co.uk <- the .co.uk is a redirected domain
Any ideas?