Sometimes fax messages you receive may be displayed as From "UNKNOWN".
The reason for this is typically because the called subscriber identification number (CSID) of the sender was not found. There is an option to enable the Caller ID of the sender, in case there is a value listed that can be displayed.
To enable the Caller ID to be sent through, please submit a request to corporatesupport@mail.efax.com.
Please note that once enabled, the "From" address of faxes that you receive in your account will prioritize the Caller ID, and if not found, it will look for and display the CSID should there be one present.
This may be most impactful to your configuration if your Intake Rules include a "From" value to determine where the inbound messages are routed.