Solutions
If you do not know the performance of the sender’s fax machine, set the following before sending a fax.
Select Fax > Menu > Scan Settings and then make the Resolution setting to set the highest quality image.
Select Fax > Menu > Fax Send Settings and then enable Direct Send.
Note that if you set Resolution to Photo but you send the fax without enabling Direct Send, the fax may be sent at a lower resolution.