No, but the problem is that the SMTP specs don&#x27;t define how to validate the cert -- for example, many deliveries will work with a self-signed certificate[0], so a MITM can just make a new certificate.<p>[0] <a href="https:&#x2F;&#x2F;serverfault.com&#x2F;questions&#x2F;579138&#x2F;is-it-ok-to-use-self-signed-certificates-for-smtp-transport" rel="nofollow">https:&#x2F;&#x2F;serverfault.com&#x2F;questions&#x2F;579138&#x2F;is-it-ok-to-use-sel...</a>