So E.g. When doing doveadm fetch -u exampleuser hdr SUBJECT Silvester HEADER Return-Path someuser@example.com

it initially outputs 13 headers (same as when using with SUBJECT Silvester only) , when piping it to "grep -i 'Return-Path'" it even found only 3 out of 13 headers containing a Return-Path at all, 2 of them different than someuser@example.com - so SAME behaviour as with search.

I tried using logical conjections of header searches and it works with my installation of dovecot, so either it's a bug introduced later than 2.1.16, or perhaps it from the different search engine you use (I use the default that comes with dovecot -- squat?).

Sorry, can't help you out further.

Joseph Tam <jtam.home@gmail.com>