I've been having an issue with the User Mailbox Backups. My environment is a Hybrid setup with the majority of mailboxes on prem. Everything was working fine until about 2 months ago. Went through CV support but they have been completely useless and are blaming it on microsoft at this point.
Exchange Server is 2016 running on Windows Server 2016.
Access node is server 2016 running Outlook 2013 SP1
The few exchange online mailboxes that we have backup without issue.
Any on prem mailboxes fail with error:
ExAgentController::SetFatalError() - Agent  Worker  reported fatal error [469762432 : Failed to initialize MAPI subsystem. Please verify that Outlook is installed and matches the bit width of the software. If Outlook is installed, try the following: 1) Reboot the machine, 2) If using a static profile, delete it and recreate it, 3) Reinstall Outlook], stop the controller
Every other operation in both CVMailBackupCoordinator.log and CVMailBackup.log appear to run successfully.
I can't find anything online. I've tried all of the troubleshooting steps in CV's documentation.
Tried everything here: https://documentation.commvault.com/commvault/v11/article?p=25627.htm
Gone through the service account setup several times. Reinstalled different versions of outlook over and over, static profiles, changed access node server. Nothing works
Readiness Check on the Mailbox client passes with all options selected.
CV is currently on 11.20.22 as I was told this would probably fix my issue.
Any info would be greatly appreciated. I am tearing my hair out over this one. Please let me know if anymore info is needed.