Office 365 / SSL / Outlook Prompts


After you switch the on-premise Exchange server to Office 365, Outlook still prompts with SSL errors (The security certificate has expired or is not yet valid)


  1. Log onto old Exchange server
  2. Run Exchange Power Shell
  3. Run Get-ClientAccessServer -Identity “[SERVERNAME]” | Format-List
  4. Ping
  5. Set-ClientAccessServer -Identity “MBX-01” -AutoDiscoverServiceInternalUri “https://RESULT_OF_PING/autodiscover/autodiscover.xml”
  6. Clear DNS server cache and restart the DNS service
  7. On client machine, run ipconfig /flushdns