Cool, just spent 20 minutes getting a proper cert from let&#x27;s encrypt, and setting postfix to opportunistically encrypt outgoing mail.<p>Used this service to make sure my setup is correct: <a href="http:&#x2F;&#x2F;www.checktls.com&#x2F;index.html" rel="nofollow">http:&#x2F;&#x2F;www.checktls.com&#x2F;index.html</a><p>Also, thunderbird apparently does not like Alternate Subject Name for smtp, but with Let&#x27;s encrypt I can just issue a mail server-specific key.