http://7fh6tueqddpjyxjmgtdiueylzoqt6pt7hec3pukyptlmohoowvhde4yd.onion/public-inbox.git/tree/Documentation/public-inbox-watch.pod
Default: none
=item publicinbox. < name > .watchheader
[publicinbox " test " ]
watchheader = List-Id: < test.example.com > If specified, L < public-inbox-watch(1) > will only process mail
matching the given header. If specified multiple times in
public-inbox 1.5 or later, mail will be processed if it matches
any of the values.