When installing or reinstalling the MSA, you get the following error:
Messaging Security Agent failed to be installed on the Exchange server: sunmail
The operation will continue until it is completed even if the window is closed.
Internal Error 2753: instISDeferredCustomActionSt
To resolve the issue:
- Open the Registry Editor (regedit.exe).
Always back up the whole registry before making any modifications. Incorrect changes to the registry can cause serious system problems.
- Delete the following registry key:
- Reinstall the MSA.