Inbound Fax Encryption

We are trying to determine if fax to email aligns with our security posture. As seen on RC documentation and inspected in Message Trace we have confirmed outbound faxes are encrypted. This part we are content with. The issue is inbound fax to email from customers/vendors that are using a physical fax machine. Once that fax is sent to RC's address we don't know what happens. Is the document faxes being encrypted before transport to our mail servers? Hopefully someone has the answer or can point to me documentation with the information.

Thanks, John