Most email on the Internet today does use TLS at present. Google's Safer Email transparency report includes metrics for the rates of inbound and outbound email

Most email on the Internet today does use TLS at present. Google's Safer Email transparency report includes metrics for the rates of inbound and outbound email encryption at Gmail, and both are about 90%. These days all major providers and software support TLS and will employ it by default. (There are some holdouts though, just like for HTTP.) [1] https://transparencyreport.google.com/safer-email/overview https://transparencyreport.google.com/safer-email/overview