dns.pool.com has one IP number. 1km.ca, por.biz, smtpd.us, a-day.us, myru.org and at least 100 other hosts use this as a nameserver. pool.com is delegated to two nameservers, however one delegated nameserver is missing in the zone. All nameservers are at pool.com themselves. They are on the same IP network. Incoming mail for pool.com is handled by one mailserver at momentous.ca. pool.com has one IP number. dns.pool.com is hosted on a server in Canada.