Brother MFC-9320CW - Manual (Page 120)

Web Based Management
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You can set Passive Mode to OFF or ON depending on your FTP server and network firewall configuration.
By default this setting is OFF. You can also change the port number used to access the FTP server. The
default for this setting is port 21. In most cases these two settings can remain as default.
Note
Scan to FTP is available when FTP server profiles are configured using Web Based Management.