Mail Submission Protocol

Jakob Schlyter jakob at
Wed Apr 21 16:56:07 CDT 2010

On 21 apr 2010, at 16.14, Leen Besselink wrote:

> We added SSL to our SMTP-service and tell our customers to use SSL (not TLS)
> with authentication and have the mailserver listen on the TCP-ports which
> the mailclients pick for that (of which their are a few if I'm not mistaken).

Assuming that you by SSL refer to a "raw" SSL-wrapped SMTP connection and with TLS refer to STARTTLS as described in RFC 3207, I would recommend against using "raw" SSL-wrapped SMTP.

Although there are some email clients that do this (and they usually use the unregistered port 465 for this), setting this up with Message Submission for Mail (as described in RFC 4409) and STARTTLS will likely give your customers a more joyful experience thanks to reasonable defaults in most modern email clients.


More information about the NANOG mailing list