Tweaking Mail-in-a-Box

Disable Greylisting

Disabling Greylisting helps to receive emails without any delay.

touch /etc/postgrey/whitelist_clients.local
nano /etc/postgrey/whitelist_clients.local

Add contents:

# Don't greylist any domain.
/.*/

Save and Exit, then:

service postgrey restart
service postfix restart

Source: https://discourse.mailinabox.email/t/disable-greylisting-modify-whitelist/137/2