reconfigure-postfix

#!/bin/bash

if [[ -z "$(hostname -d)" ]]; then
    echo "Set up FQDN first!"
    exit 0
fi

echo "postfix postfix/mailname string $(hostname -f)" | debconf-set-selections
echo "postfix postfix/destinations string \$myhostname, $(hostname -s), localhost" | debconf-set-selections

echo $(hostname -f) > /etc/mailname

postconf -e "myhostname= $(hostname -f)"
postconf -e "mydestination= \$myhostname, $(hostname -s), localhost"

postconf -e "compatibility_level= 2"

service postfix reload