The connection line is set to PSTN in a facility where a private branch exchange (PBX) is being used.
Solutions
Select PBX in Settings > General Settings > Fax Settings > Basic Settings > Line Type on the control panel.
Your caller ID is blocked.
Solutions
Contact your telecommunication company to unblock your caller ID. Some phones or fax machines automatically reject anonymous calls.
The header information for outgoing faxes is not registered.
Solutions
Select Settings > General Settings > Fax Settings > Basic Settings > Header and set up the header information. Some fax machines automatically reject incoming faxes that do not include header information.
