Re: [ietf-smtp] Endless debate on IP literals

[Keith Moore <[e-mail]>]

On 1/1/20 11:01 AM, John R Levine wrote:

> I'm thinking, for example, of DMA (Dragonfly Mail Agent), a small
> almost MTA that I use on my small server boxes.  Even though DMA can
> technically do all the things that 5321 says an MTA is supposed to do,
> I have it configured to relay everything to the submission server on
> my real MTA rather than trying to send mail directly. 

I've been wondering if there's a need to talk about (for lack of a 
better term) "pre-submission relaying" which happens when a message is 
(for whatever reason) not initially submitted to a real submission 
server that does whatever sanity checking and fixup are needed to make 
the message suitable for relaying into the global email system.

The next thing I wonder is what port should be used for pre-submission 
relaying, or whether there should be a separate port for that, or 
whether there's a need for in-band signaling to tell an MTA which role 
it is supposed to play for a particular transaction.   (Somehow I don't 
think yet another port is a good idea, as I suspect that it just has the 
effect of giving people more confusing configuration choices to make).

But part of the notion of submission is to do all of that fixup in one 
place, so you don't have multiple MTAs in the signal chain mucking with 
the message.   It would be convenient if that fixup were unambiguously 
to be done at the first hop, but it seems that we might not have the 
luxury of being able to mandate that.   So to my mind the question then 
becomes, how do we unambiguously indicate where that fixup is to be 
done, so that it is only done once?

Keith