Select your fax driver as the printer, and it will ask for phone number. Fax uses line art mode, it is NOT optional. If you don't use line art, the fax driver will convert it sight unseen to line art. You may prefer to see this before you send it. Read the previous section about Threshold in line art mode .
Threshold is very important to scanning for fax.
I suspect 203 dpi comes from 8 dots per mm today. Fax is a very old specification, primitive almost, surely our oldest, and goes back to when the facsimile paper was attached to a rotating cylinder and marked with a vibrating ink pen. You should scan at 200 dpi line art mode for fax. WinFax Pro accepts only 200 dpi. 200 dpi is always correct.