deliver(1) on Linux
The text b1cc5c52e6eb, as Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster) shipped it.
Dovecot's local mail delivery agent
Flags it lists
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-a -
-c -
-d -
-e -
-f -
-k -
-m -
-o -
-p