over in id:87mug6kyyv.fsf@fifthhorseman.net i started looking at the
ways that notmuch sometimes synthesizes a message-id.

In previous discussions around it,  (e.g. in NEWS about notmuch 0.17)
it's assumed that the form of the message-id itself -- it starts with
"notmuch-sha1-" -- should be sufficient to distinguish such a message
from a non-synthesized messaage.

But, a mail user agent is typically well-served by paranoia -- an
external malicious party can of course generate a message myself with
such a message-id (e.g. this message).

The pattern that we've been gradually establishing is that when notmuch
itself does some unusual processing on a specific message, it notes the
fact of that processing in a property on the message object (cf
notmuch-properties(7)).

It would make sense to set such a property when synthesizing a
message-id, i think.  I don't have time to implement this myself right
now, but i thought i'd record it here on the mailing list as a feature
request.

Maybe someone looking to cut their teeth on the notmuch codebase with a
relatively well-defined task could suggest a patch?

             --dkg