looking for a solution to send emails in SSL

Hello, almost all internet service providers are or switch to SSL/TLS... (Finally in France for the rest of the world, I'm not sure) Only Gmail via sendgrid for the moment remains unencrypted, but you cannot send attachments with this service! I work with Arduino Mega and w5500 Ethernet shields. So my question is this impossibility of using SSL/TLS does it come from the hardware (shield or Arduino?) or from the libraries? I must admit that I don't understand the subject at all... In my research I came across this article: https://github.com/OPEnSLab-OSU/SSLClient Would this be a solution? Or other things? Does anyone have a solution? THANKS