Upgrade and downgrade instructions

To upgrade MailerQ from version < 5.7 to 5.7+

Debian/Ubuntu:

sudo apt update
sudo apt install -y mailerq
sudo mailerq --repair-database

CentOS/RHEL:

yum update
mailerq --repair-database

To downgrade MailerQ from version 5.7+ to 5.6

Debian/Ubuntu:

sudo apt-get install -y --allow-downgrades mailerq-5.6
sudo mailerq --repair-database

CentOS/RHEL:

yum remove mailerq-5.7
yum install mailerq-5.6
mailerq --repair-database