You probably read my post too quickly Arend - that is the article that I pointed to in my post lol. I have read that, but I actually agree with the comments by that guy on that page.
LOL, sorry about that, yes I did read too quickly :-)
But seeing as IANA revoked 465 I would personally go with port 587.
"465 TCP URL Rendezvous Directory for SSM (Cisco protocol) Official"
"465 TCP Simple Mail Transfer Protocol over TLS/SSL (SMTPS) Unofficial"
See: https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers
