Problem this snippet solves: iApp for setting up SMTPS and/or straight SMTP. This is just an extended version of the SMTP iApp with added SSL support and improved monitoring. Contains contributions ...
If you opt not to permit insecure SMTP you'd obviously force STARTTLS on port 25 (and port 25 would then be configured the same as 587). It seems like the client manages to send their credentials before they get the message that it's not allowed anyway, which is why port 465 is my favorite and should be promoted as the preferred SMTP option for clients to use.