Do the following, in order, on the Exchange Server:
1. Disable IRM: "Set-IRMConfiguration -InternalLicensingEnabled $false"
2. Backup and delete the directories in "C:\ProgramData\Microsoft\DRM\Server"
Note: The Server folder is a hidden system folder and you will need to uncheck the "Hide protected operating system files" to view the folder.
4. Enable IRM: "Set-IRMConfiguration -InternalLicensingEnabled $true"
5. Test IRM: "Test-IRMConfiguration -sender [[email protected]domain.com
If the above solution does not work, do the following:
On Exchange CAS Server, go to C:\ProgramData\Microsoft\DRM and grant "Network Service" account modify access. (Right-click, select Properties and Security)