How would they know? If using email-to-fax, I think that the coverpage or the TO part shows "
outgoingnumber@rcfax.com" or similar as the fax number, so the person that receives it can figure out that it comes from RC. I think you can change that behavior by using a name with the address like "outgoingnumber <
outgoingnumber@rcfax.com>" and then it just shows outgoing number (or whatever you replace there).
Insecure? It's possibly the email part of it that they consider to be insecure, if you are using email to send the faxes, not the fax part of it being insecure. The email part could be secure, though, if both the sender and the receiver of the email allows SSL/TLS email connections. RC sends email out over a SSL/TLS connection if the receiving side supports it, I assume they also accept SSL/TLS connections as well, but so far I have only confirmed the emails sent from RC, not the emails received by RC. I haven't done any outgoing email-to-fax yet, only incoming fax-to-email.
