Ruby on Rails ActionMailer SMTP Settings mTLS

Question

How would you setup a mTLS connection for action mailer in ruby on rails?

Answer 1

ActionMailer leverages the Mail gem to sent mails via SMTP, which in turn uses the net-smtp gem.

Now, while the net-smtp gem in principal supports to configure mutual TLS by specifying custom parameters for its SSLContext, this capability is not exposed by the Mail gem and thus is not available directly to ActionMailer.

Thus, it is currently not possible to configure mutual TLS with the Mail gem nor with ActionMailer out-of-the-box.