HP laserjet m1212nf - Manual (Page 167)

Faxes are being received very slowly.
Cause Solution
The fax might be very complex, such as one with many
graphics. Complex faxes take longer to be received. Breaking longer
faxes into multiple jobs and decreasing the resolution can
increase the transmission speed.
The resolution at which the fax was sent or is being received
might be very high. To receive the fax, call and ask the sender to lower the
resolution and resend the fax.
The fax is being sent via an international call. Allow more time to transmit fax jobs internationally.
ENWW Solve fax problems 153