Opportunistic SSL/TLS encryption on outgoing emails

Rob Mueller – 28 January 2010

Early last year, we implemented opportunistic encryption of incoming emails. We’ve now done the same thing for outgoing emails. This means that for email sent via FastMail (either the web interface or SMTP), if the receiving server advertises STARTTLS support in response to an EHLO command, we will try and negotiate a secure connection and send the email over a secure connection. However if the negotiation fails for any reason, we’ll fallback to a standard connection.

Some extra notes on this:

Since this feature is only enabled if the other side advertises support for it, it shouldn’t affect sending to servers that don’t support STARTTLS, and thus shouldn’t affect the deliverability of email in any way.