feature request: caching message arrival time

[Ralph Seichter]

* Daniel Kahn Gillmor:

> Since notmuch actually knows when it recieved the message [...]

Not meaning to complicate things, but Notmuch does not receive messages
at all. ;-) One needs to rely on some software to populate the Maildir
tree (Dovecot LMTP in my case, Postfix or some other MTA for local
delivery in other cases). Any software transporting the raw messages
can, and sometimes must, manipulate the header data, and the order in
which files within the Maildir tree are created is also not determined
by Notmuch.

As an example: My nightly backup script disables local delivery for the
duration of the backup process. Once reactivated, delivery of queued
messages resumes, but it is not guaranteed to happen in the order of
arrival. So even the local MTA, although trusted, might induce issues in
terms of delivery time.

-Ralph