When performing a journal archive migration to Enterprise Vault 10.0.4, the following may be logged from time to time and be shown on the Failed Items screen:
Error Text: Operation not supported. Details: Not implemented (0x80004001) (Count=407) Error Text: This does not seem to be a Journal Message. Aborting.
This is a Symantec Enterprise Vault issue which can be resolved by upgrading to Enterprise Vault 10.0.4 Cumulative Hotfix 2, or later.