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71GA

Member

From: Slovenia

Registered: 2012-09-15

Posts: 282

[SOLVED] Email "submission" and "relay" event

I am setting up a postfix server on Arch and I want to get to the bottom of the term email "submission" and "relay". So what does this really mean?

In my  head I have two possible scenarios:

SCENARIO 1

What the terms mean is:

- "relaying" ⟹ "event of sending email using SMTP protocol"
- "submission" ⟹ "event of recieving using SMTP protocol"

In this scenario I have to always tell who in the email chain I am refering to.

SCENARIO 2:

What the terms mean is:

- "relaying" ⟹ "event of email  passing through any device using SMTP protocol (email is recieved & sent ie. forwarded)"
- "submission" ⟹ "event of sending using SMTP protocol"

So which scenario is correct?

Last edited by 71GA (2020-12-22 18:49:28)

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C, ARM, ARM assembly, HTML, CSS, JS, Linux

Trilby

Inspector Parrot

Registered: 2011-11-29

Posts: 30,330

Website

Re: [SOLVED] Email "submission" and "relay" event

I think scenario 2 is closer: certainly for "relaying" that sounds spot on.  Relaying was first - that was the job of the server: relay outside mail to internal recipients and internal mail to outside recipients.  Submission came later as people who might belong "inside" would connect from the "outside" (e.g., an employee of a company working from home and using the company email server to send their mail).  Submission can be thought of as a superset of relaying: the server relays submissions, but it does much more than just relay for a submission.  Submitted emails (but not relayed) may require authentication and may be rewritten.

So I'm not sure about "the even of sending using SMTP protocol" as your defintion.  That may be the client / user's perspective, but for the server, submission is relay but with a few checks and potential modifications of the message first.

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"UNIX is simple and coherent" - Dennis Ritchie; "GNU's Not Unix" - Richard Stallman

Zod

Member

From: Hoosiertucky

Registered: 2019-03-10

Posts: 634

Re: [SOLVED] Email "submission" and "relay" event

An email system consists of the following modules...

[Client]
MUA--Mail User agent (Thunderbird)

[Mail Server]
MSA--Mail Submission Agent
MDA--Mail Delivery Agent
MTA-- Mail Transfer Agent

The MSA recieves an email from the MUA and checks it for format, errors and valid sender/reciever then either responds as undeliverable or hands it off to either the MDA or the MTA (for relaying). MTAs' can also respond as undeliverable

The MTA will relay the email to either another email server MTA within the enterprise where it will be handed off to the MDA or it will relay it to an Edge MTA for forwarding on to a destination MTA over the Internet according to DNS MX records.

The MDA stores the email until an MUA requests to read it (pushed to the client or just read on the server)

RFC 2476 message submission.

MTA wikipedia

Last edited by Zod (2020-12-19 01:37:08)

Lone_Wolf

Administrator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 13,281

Re: [SOLVED] Email "submission" and "relay" event

Zod nails it.

Incase you want some background info how/why this happened, check https://en.wikipedia.org/wiki/Simple_Ma … ol#History .

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71GA

Member

From: Slovenia

Registered: 2012-09-15

Posts: 282

Re: [SOLVED] Email "submission" and "relay" event

Trilby's answer helped me the most. Thank you very much!

Last edited by 71GA (2020-12-20 19:13:47)

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C, ARM, ARM assembly, HTML, CSS, JS, Linux

GSMiller

Member

Registered: 2020-11-23

Posts: 75

Re: [SOLVED] Email "submission" and "relay" event

Trilby's answer helped me the most. Thank you very much!

Yes, he is great.
Please pu t the word SOLVED to your title.

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