Best practice for SMTP relay with user authentication

[Per olof Ljungmark]

Erik Norgaard wrote:
> Hi:
> 
> I have my postfix authenticate users before accepting mail for non-local 
> delivery. Till now, users can connect to port 25 and 465 (smtps) use 
> STARTTLS and authenticate.
> 
> But, I stumbled upon submission port 587 which is not reserved - it 
> appeas - for a protocol but for a use?
> 
> I'd like to align my configuration with best practice. Should I just 
> move postfix to bind to port 587 or did I misunderstand that submission 
> is indeed a different protocol? Is there any best practice for which 
> protocol should be used for submission?

I'm not an authority on the subject but we use it here for 
server-to-server. Here's a link to more reading:
http://www.faqs.org/rfcs/rfc2476.html

We use port 465 for authenticated MUA-to-MTA.

Per olof