mutt: fix a minor bug in smart filtering
mutt: fix a minor bug in smart filtering

We weren't getting the initial request email archived. I originally had
this working like this (with `Message-ID`) before, but I inspected the
headers and thought this would do the same. But it doesn't, and on
re-inspecting them, I can't see any examples that would work.

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent