Every single registered domain name has at least two Name Server records which show where it is hosted i.e. by using these records you direct your domain to the servers of a specific web hosting provider. That way, you have both your site and your e-mails handled by the exact same company. On the lower level of the Domain Name System (DNS), however, there are a number of other records, for instance A and MX. The former shows which server manages the website for a given domain address and is always an IP address (220.127.116.11), while the latter shows which server manages the e-mails and is always an alphanumeric string (mx1.domain.com). For example, whenever you type a domain in your web browser, your request is directed through the global DNS system to the provider whose NS records the domain address uses and from there you will be directed to the servers of a different company if you have set an IP address of the latter as an A record for your Internet domain. Having different records for the website and the emails suggests that you could have your website and your emails with two different companies if you would like.