Regulated industries such as government, finance, and healthcare have always preferred fax for transmitting sensitive documents, because it’s more secure than email or post. But with traditional fax machines, transmissions via phone lines aren’t encrypted—and when the fax is printed out, an unauthorized person could walk by and pick it up.
Trustworthy internet faxing services have security protocols built in. For example, RingCentral sends faxes securely over an encrypted connection (TLS) and lets you store them in a password-protected account. You can also customize your personal security controls.