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Quick: Exchange 2013/2016 upgrade to latest CU (Cumulative Update)

  1. Document Exchange Service Settings
  2. Backup any OWA or service customizations
  3. Export out all IIS Pool and Site Configuration Settings
  4. Export out all Exchange Service Settings
  5. Take a backup.
  6. If you have an anti-spam solution disable connectivity in your firewall from the Ant-spam solution (Symantec Cloud, Email Laundry, Mimecast) to your Mail Server.  If any external client sends you an email during the maintenance period the email will be held by the anti-spam solution until the Exchange server is back online. (not necessary if you have multiple exchange servers in a DAG)
  7. Backup Mail Logs
  8. Restart Server
  9. Ensure .net 4.7.1 is installed, if not install it.
  10. Install CU 21 via Run As Administrator CMD Prompt.
  11. Reboot when prompted
  12. Ensure all services, customization, IIS pools are running and configured properly.
  13. Re-Enable Anti-spam rules to ensure mail flow and to drain the mail queue.