North American Network Operators Group
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Re: Lazy network operators

  • From: Joe Abley
  • Date: Wed Apr 14 10:18:55 2004 
On 14 Apr 2004, at 04:09, Miquel van Smoorenburg wrote:


That was solved 6 years ago. You let them use port 587 instead of 25.
http://www.faqs.org/rfcs/rfc2476.html
There's a slight wrinkle with that for people who want to submit mail over SSL.

Several graphical, consumer-grade mail clients let you select a port for "outgoing mail (SMTP)" and also have a checkbox for "use a secure connection (SSL)".

If (port == 25 && use_ssl) the client will EHLO to 25/tcp, and will attempt to use STARTTLS in order to encrypt the session.

If (port != 25 && use_ssl) the client will assume an SSL-wrapped SMTP server on the other end, and will not use STARTTLS.

If (port != 25 && !use_ssl) the client will assume a non-SSL-wrapped SMTP server, and will not use STARTTLS.

This provides an operational/support issue for people running mail servers who want to support both SSL and also non-encrypted mail submission for their clients. It's an implementation problem in mail clients, not a protocol issue, but since it sounds like it might make the helpdesk phone ring, I thought I'd mention it.


Joe