To solve the problem of not sending/receiving email on a server using the MSFE / Mailscanner utility, use the following commands:
cd /root
wget https://download.configserver.com/msinstall.tar.gz
tar -xzf msinstall.tar.gz
cd msinstall
sh uninstall.sh
rm -rf installer
Make sure to activate the MSFE license after the installation on the cPanel/WHM server.