If you use the ON/OFF key to turn the Brother machine off, then your settings and stored faxes will remain in the machine's memory.

If you turn the Brother machine off by unplugging it or the machine loses power in an electrical outage, your stored faxes will be lost.

However, you will not lose the settings you have chosen using the Menu key because they are stored permanently.
Also, you will not lose your settings in the FAX, COPY and PHOTO CAPTURE mode key menus if you have chosen Set New Default.