A fax between two machines is a single telephone call from one number to another, with no server in between to store a copy, which is the property that made regulators comfortable with it and that ordinary email does not have: an email passes through several servers, is stored on each, and can be forwarded without limit. That is the sense in which fax is more secure than email. It is not the whole story, because a fax that prints on a shared machine is as exposed as any paper on a desk, and because an online fax service reintroduces a server, which is why the service's own safeguards and its business associate agreement matter. The Fax Line Index records which vendors state that agreement on the plan priced.
Where fax is more secure
The transmission is point to point, over the telephone network, between two identified numbers, and it leaves a transmission report on both ends. There is no inbox to phish, no attachment to forward to the wrong list, and no copy sitting on a mail server for years. For a legal document or a medical record that must reach one named recipient, that shape is why courts, insurers and clinics accepted fax long after email arrived, and why HIPAA has always treated fax between covered entities as a permitted transmission.
Where fax is less secure
A fax that arrives on a paper machine in a shared office is readable by whoever walks past, and a misdialled number delivers it to a stranger with no bounce and no warning. Neither risk is theoretical; both are the reason a confidentiality notice sits on the cover and the recipient's number is verified before sending. Email, by contrast, can be encrypted end to end and its delivery confirmed to a named mailbox, so a well-run encrypted email system is not less secure than a badly run fax machine.
What an online fax service changes
It puts a server back in the middle, storing the fax as a PDF and delivering it to an inbox, so the point-to-point property now depends on how the provider stores and protects it. That is what the business associate agreement binds a provider to for protected health information. WestFax prints a signed BAA on every plan at $14.99 a month for Solo; eFax prints one on its Business plan; Documo prints HIPAA compliance included on Solo at $25 a month billed annually. A service that states it is more secure than a machine on a shared desk; a service that does not state it is a question to ask before the first patient record goes through.
Questions people ask about is fax more secure than email
Is faxing safer than emailing?
A machine-to-machine fax is a point-to-point call with no stored copies in between, which email lacks. A fax on a shared paper machine or a misdialled number is not safe at all; the safeguards around it decide.
Is online fax secure?
It depends on the provider's storage and its agreement to protect what it stores. For health information, choose a vendor whose page states a BAA on the plan you buy; the HIPAA class page lists them.
Why do doctors and lawyers still fax?
Because the point-to-point transmission and the report on both ends satisfied regulators and courts decades ago, and the online services kept the report while removing the machine.