[horde] [SOLVED] Error connecting to smtp server

Jens-U. Mozdzen jmozdzen at nde.ag
Mon Sep 2 15:18:36 UTC 2013

Hi Michael,

Zitat von Michael M Slusarz <slusarz at horde.org>:
> Quoting "Jens-U. Mozdzen" <jmozdzen at nde.ag>:
>> Zitat von Michael M Slusarz <slusarz at horde.org>:
>>> [...]  Further, everyone should be using authentication to the  
>>> SMTP server.  The days of sending via open SMTP relays (should  
>>> have) long since passed.
>>> michael
>> not within corporate setups. Identifying local systems by IP is  
>> often considered sufficient (and I wouldn't disagree).

To be clearer: I'm referencing the "The days of sending via open SMTP  
relays..." above. STD 72 isn't as widely adopted as some do wish, at  
least not in it's new definition of the submission port.

> You are incorrect.  This exact usage is defined for MSA's in the  
> RFC.  See, e.g. RFC 6409 [4.3]:
> "...unless it has already independently established authentication  
> or authorization (such as being within a protected subnetwork)."
> You should never ever ever ever ever insert mail into the message  
> delivery stream via port 25.

I agree that one "should" use port 587 to better distinguish between  
MSA and MTA, but practice shows that port 25 is still used a lot for  
that, especially in corporate setups with strongly controlled internal  
networks. Maybe that's why its use is covered by section 3.1 of RFC  
6409: "A site MAY choose to use port 25 for message submission by  
designating some hosts to be MSAs and others to be MTAs."

De facto, many corporate environment have been using MSAs (without  
calling them MSA) since implementing SMTP-based email so many years  
ago... setting up an internal MSA (accepting submissions based on IP  
address or some different authentication scheme) and using a separate  
MTA infrastructure for, well, mail transport. Many just have not  
switched to using the new port - but as said above, they're covered by  
STD 72 / RFC 6409...


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