Any active domain which is added in a hosting account features a number of records that enable it to work properly. In the typical case, the name servers (NS records) show where the domain is hosted and they are set on the side of the registrar company, but on the lower level there are particular records created through the hosting company like A (IP address of the website/server), MX (e mail server), SRV (employing an Internet domain for non-website purposes on a specific port number like Voice-over-IP), and many others. With access to these records and by being able to edit them, you may have your site with company A and your e-mails with company B, for example. This offers you more overall flexibility because you can select the best provider for each of these services and you do not have to stick to one company. As soon as you select a hosting company, you have to make sure that you have access to all DNS records freely since some providers have an extra fee for this feature.