> Have you actually come across any case where a *proper* non-spam message is sent without a message-id and passes
throughactual mailservers on the way?
>
> Looking through the approximately 1.4 million mails in the postgres list archives, not a single one has a message-id
generatedby the archives server MTA (which is configured to generate it). Not a single one by our inbound relay
servers.And exactly one by the pglister server -- which turns out to be a bounce that ended up in the archives because
ofa misconfiguration back in 2018 that's not visible in the public archives.
After some tests, I do have a very few number of non-spam examples (3 emails from 2 different people in a
postfix+mailmanmbox of 5k emails), but they date from 2003-2007.
Exim already handles empty Message-IDs by default by generating them [1], although it will let a message with
Resent-Message-IDpass through as-if. I tested such a case, and pglister seems to actually drop the message (or fail
silently).
[1]: https://www.exim.org/exim-html-current/doc/html/spec_html/ch-message_processing.html#SECID226
--
Célestin Matte
