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

2020-01-01 10:30:40
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?


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