The M-Files Flag
The M-Files flag shown in the classic Microsoft Outlook message listing tells that you have already saved the message to M-Files.
If another user (for example, another recipient) has saved the same message to M-Files, M-Files confirms whether to save that message again. Even if you do not save the message again, the M-Files flag will now be shown in the classic Microsoft Outlook for that message.
With the Update M-Files Status function in the context menu of the message, you can easily show all M-Files flags. Also messages saved in M-Files by other users will then have an M-Files flag.