Amazon SES, Message-ID and mailman

Question

Hi,

We are running a mailman 2 mailing list, and recently switch the mail gateway from another company to now use Amazon SES.
There's a new problem that the mailman archives are not able to group threads together the way they were before.  Users are complaining about issues in their local mail clients.
It seems to be related to the mail header fields Message-ID: , References: , and In-Reply-To: .
If Amazon SES rewrites the Message-ID, it won't match the original Message-ID, and so the second email won't be matched with the first email in the web archives display.  Addtionally, replies are often sent both to the list and to individual participants, and it's critically important that both of these copies have the identical message id.

Is there a way to have Amazon SES not modify the Message-ID header?   Or, any other solution to this particular problem?

Thanks,
Sam

jcsanyi · Accepted Answer

SES will always rewrite the outgoing `Message-ID`, but it leaves the `References` header alone - so if you append the original `Message-ID` to `References` before the message hits SES, the recipient's reply will continue to carry the original `Message-ID` in its `References` chain - and Mailman's archive should be able to match the replies back to the original.

I wrote a small Postfix milter that does exactly this: [milter-autoref](https://github.com/jcsanyi/milter-autoref) ([Docker image](https://hub.docker.com/r/jcsanyi/milter-autoref)). It doesn't have anything in it that's specific to Mailman, but if Mailman is sending messages via Postfix which forwards to AWS SES, adding this to the Postfix installation should fix the issue. (Disclosure: I'm the author.)

This should work as long as Mailman is sending messages through a local Postfix installation, not relaying straight to SES SMTP.

sdarwin · Answer

@jcanyl very clever! In the absence of this fix, years ago, we switched to another product, but certainly wanted to use SES.

Riku_Kobayashi · Answer

The following document shows "Message-ID" in the header field, so it is possible to send an email with the same ID.  
https://docs.aws.amazon.com/ses/latest/dg/header-fields.html

As described in this document, you can use "SendRawEmail" and include "Message-ID" in the header to send an e-mail with an arbitrary value.  
https://docs.aws.amazon.com/ses/latest/dg/send-email-raw.html  
https://docs.aws.amazon.com/ses/latest/dg/send-email-concepts-email-format.html#send-email-concepts-email-format-header

Amazon SES, Message-ID and mailman

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