doveadm-flags(1) on Linux
The text 6f674450d75e, as Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster) shipped it.
add, remove or replace messages' flags
Flags it lists
-
-A -
-D -
-F -
-S -
-o -
-u -
-v