For private domain email address, you need to have a premium account; also you must own a domain name as DriveHQ doesn't sell domain names.
You should add an MX record to your DNS. Dynamic DNS is not tested and probably doesn't work. However, almost all domain registrar companies also offer free DNS service for your domain. Please use their website (domain management pages) to add an A-Record and an MX-record. The MX record should point to DriveHQ email hosting server: 18.104.22.168.