After checking and verifying pretty much every solution to the now well known public domain name SSL cert vs. internal .local domain name problem, I'm stumped to find a fix for my client's EX2013 environment.
1. Bought and installed SSL Plus cert from digicert.com: mail.domain.com
2. Internal AD domain was previously configured as domain.local
3. Internal EX2013 server (W2K12R2) host name is ex01.domain.local
4. Changed IIS bindings for Default Site from self-signed cert to the digicert.com cert for 443 * All Unassigned
5. Added DNS zone on DC (W2K12R2) of domain.com (and reverse lookup zone to match)
6. Added host A record of 'mail' to new domain.com zone pointing to internal IP of ex01.domain.local
7. Added host A record of 'autodiscover' to new domain.com zone pointing to internal IP of ex01.domain.local
8. Ran digicert.com's Internal Name Change Tool which basically just runs the following EMS commands and then recycles the app pools:
Set-ClientAccessServer -Identity CAS_Server_Name -AutodiscoverServiceInternalUri
Set-WebServicesVirtualDirectory -Identity "CAS_Server_Name\EWS (Default Web Site)"
Set-OABVirtualDirectory -Identity "CAS_Server_name\oab (Default Web Site)"
9. Verified above using the corresponding Get commands in EMS.
10. Verified mail.domain.com cert is valid and assigned to IMAP, POP, IIS, SMTP services in EX2013 EAC.
11. Restarted the EX2013 server just to be safe.
12. Fired up Outlook on a workstation, got the same 'There is a problem with the proxy server's security certificate. The name of the security certificate is invalid or does not match the name of the target site ex01.domain.local'.
After this I verified Outlook can still sending emails internally to other mailboxes on the same EX2013 server.
So how do I get rid of this error message everytime we start Outlook?