Upgrade and downgrade instructions

To upgrade MailerQ from version < 5.8 to 5.8+

Debian/Ubuntu:

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

CentOS/RHEL:

yum update
mailerq --repair-database
systemctl restart mailerq

To downgrade MailerQ from version 5.8+ to 5.7

Debian/Ubuntu:

sudo apt-get install -y --allow-downgrades mailerq-5.7
sudo mailerq --repair-database
sudo systemctl restart mailerq

CentOS/RHEL:

yum remove mailerq-5.8
yum install mailerq-5.7
mailerq --repair-database
systemctl restart mailerq