Email is fundamentally insecure. There are such a plethora of issues with it, it is crazy to think about the kind of information sent with it. It is probably even crazier when you realize we’ve had a solution for sending secure email since 1991.
If you have someone’s public SSH key, you can use OpenSSL to safely encrypt a file and send it to them over an insecure connection (i.e. the internet). They can then use their private key to decrypt the file you sent.