We pick d.root-servers.net, one of the 13 root servers (1), and ask it about tucows.info and learn that info is delegated to six name servers (2), so we ask c0.info.afilias-nst.info where we learn that tucows.info is delegated to three name servers, including dns2.tucows.com (3), so we ask that one and get the following answer:
Tucows.info is a domain controlled by three domain name servers at tucows.com. Two domain name servers have the same IP number. Both are on different IP networks. Incoming mail for tucows.info is handled by one mail server also at tucows.com. We are missing the IP:s of one server: mail.tucows.com. Tucows.info has one IP number (216.40.32.30).
About one in six of them use only the mail server mail.tucows.com. Worth noting is that most of the domains that only use the mail server mail.tucows.com use name server group 1.
The mail server mail.tucows.com only
There are about thirty domains that only use the mail server mail.tucows.com.