Description

See #3732 (comment).

Original feedback to #3732:

Just a thought.

I'm not sure if this would work, but it might be possible to provide an explicit Message ID header (swaks has an option for adding headers), and that may be traceable in the Postfix logs.

If not, I think it persists when it arrives to Dovecot storage, and could be used to find the mail exists on disk 🤔

We should implement this, or at least investigate, but not in #3732.