Error

The following warning is shown in the detailed log when attempting an MS Exchange mail-level backup:

[BackupRequestTask._uploadFiles] Unexpected Exception: [Error] CExMAPI::SaveToMessage::SaveToMSG ERROR=MAPI_E_CALL_FAILED Detail=Unspecified error

Cause

This error appears to be caused by a bug in releases < 6.13.2.0.

Resolution

Update the backup agent to the latest release by performing an in-place install over the existing software.