Office 365 / SSL / Outlook Prompts

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Problem:

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)

Solution:

  1. Log onto old Exchange server
  2. Run Exchange Power Shell
  3. Run Get-ClientAccessServer -Identity “[SERVERNAME]” | Format-List
  4. Ping autodiscover.yourdomain.com
  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