Brother HL-7050N - Manual (Page 133)

4 - 6 OPTIONS
HL7050_US_UG_FM5.5
Mailbox unit
The Mailbox unit is an optional device that can be installed on the
HL-7050 laser printer to allow you to direct your printouts to any bin
that you want.
Figure 4-3
To install the Mailbox unit, please see the User's Guide that we have
supplied with the Mailbox.
Mailbox
This setting allows you to direct your printouts to any bin that you
specify.