Mail Submission Protocol

Wed Apr 21 22:17:28 UTC 2010

On 4/21/2010 6:49 AM, Claudio Lapidus wrote:
> So we are considering ways to further filter this traffic. We are evaluating
> implementation of MSA through port 587.

RFC 5068, Email Submission Operations: Access and Accountability Requirements, 
is a BCP.  It specifies authenticated port 587 for email submission across the 
net.

As others have noted, it works well through a wide variety of access 
environments.  I don't remember the last time I found it blocked.  I use it over 
TLS, of course.

Blocking of outbound port 25 for all hosts not explicitly authorized has become 
common.  The fact that 587 default to authenticated is the win.

d/
-- 

   Dave Crocker
   Brandenburg InternetWorking
   bbiw.net