You just finished setting up your MX server and everything works fine. And now you are wondering whether you need a secondary MX server for backups. Some would say that these days you actually don’t need a secondary MX server, because MTAs (mail transfer agent) queue mail if MX server is down. In addition a secondary MX server might be abused by spammers. But just for fun, let’s assume you want to have a backup MX server. And you are lucky enough to have a friend who also runs an MX server which he is willing to configure as your backup server.