The faxed document
Email to fax
Email to fax is a service that converts an email and its attachments into a fax, then sends it to the recipient's fax number.
The user writes to an address built from the fax number at the provider. A gateway receives the message, converts the attachments into a fax image, dials the number and usually sends back a report by email. Standards describe this address format, but each provider applies its own rules.
Why it matters for fax
This way of sending adds an intermediary and a conversion between the document and the line. The layout of an email body or an office file is not always preserved; a flattened PDF remains the format that guarantees the recipient gets what the sender saw.