sb_imapfilter(1) on Linux
The text 4131de858ca9, as Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it. The page shows this text now.
An IMAP filter
Flags it lists
-
-P -
-b -
-c -
-d -
-e -
-h -
-l -
-p -
-t -
-v