On Thu Mar 28 2019 17:04:37 GMT-0400 (Eastern Standard Time), Patrick
Mahan via dovecot <dovecot@dovecot.org> wrote:
> Hmm, actually it is set -
>
> root@ns:/usr/local/etc/dovecot # dovecot -a | grep auth_username_format
> auth_username_format = %Ln

Use doveconf, not dovecot (although they may do the same thing).

doveconf -a just shows you ALL settings, regardless of whether or not
they are set in your particular config.

doveconf -n shows you the settings that your running dovecot is actually
using.