We use the External Domain URL for OWA when we purchase SSL Certificate.
But the issue can come out when your Internal URL and External URL of Exchange Server are different.
The issue is user will get security alert pop-up when he/she open outlook client everytime.
To get rid of this issue, we need to change the Internal URL of OWA on Server.
First, run the Exchange Management Powershell as Administrator.
"Use Get-ClientAccessServer | FL" command to collect existing configuration for revert back if something goes wrong.
Next, use "Set-ClientAccessServer -Identity CAS_Server_Name -AutodiscoverServiceInternalUrl https://mail.ictformyanmar.com/autodiscover/autodiscover.xml" command and change the URL accordingly.
Only High-lighted text are need to aware as yours.
After that, go to Exchange IIS Manager and select Application Pools. Then right click on MSExchangeAutodiscoverAppPool and click Recycle.
Fine. We are done!
You can re-check by using Get-ClietAccessServer | FL command to ensure changed URL.
If everything is fine, just close and open the outlook client at user's PC and you won't see any secrutiy pop-up regarding Certificate.
I've use ClientAccess service only on my Server.If you use WebServicesVirtualDirectory, OABVirtualDirectory and UMVirtualDirectory, you also need to change the URL for these too.
My server is Microsoft Exchange Server 2007. Powershell command is different and depends on Server Version. So, do not forget to reference Microsoft Powershell Technet Website.
May you all be happy.
(Be knowledgeable, pass it on then)