To upgrade MailerQ from version < 5.4 to 5.4+
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 5.4+ to 5.3
Debian/Ubuntu:
sudo apt-get install -y --allow-downgrades mailerq-5.3 mailerq=5.3.2
sudo mailerq --repair-database
CentOS/RHEL:
yum remove mailerq-5.4
yum install mailerq-5.3
mailerq --repair-database