Brother MFC-J4710DW - Manual (Page 76)

Internet fax (For MFC models) (Available as a download)
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7
Error mail
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If there is a mail delivery error while sending an Internet fax, the mail server will send an error message back
to the machine and the error message will be printed. If there is an error while receiving mail, an error
message will be printed (Example: “The message being sent to the machine was not in a TIFF-F format.”).
To receive the error mail properly, you must switch Header in the Setup Mail RX to All or Subject+From+To.