Send Low-resolution faxes

Faxes are, by default, created at a high-resolution setting. Check ON to send as standard low-resolution.

Reverse fax image

Check On/Off to switch between white-on-black ground and black-on-white background. 
There is a similar option in the Fax Server application.

Scale images to fit fax machine

Scale the images to the fixed size that hardware fax machines require. 
This isn't required if you only fax to digital fax receivers.