A mail exchanger record (MX record) is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value used to prioritize mail delivery if multiple mail servers are available.

The set of MX records of a domain name specifies how email should be routed with the Simple Mail Transfer Protocol (SMTP).

Email forwarding generically refers to the operation of re-sending an email message delivered to one email address on to a possibly different email address.

The term forwarding has no specific technical meaning.

Premium email is a marketing term used by for-pay email services.

Many free email services are supported from advertising revenue.

Premium service may charge a fee for removing advertising from the service, and may have increased storage and other features, such as virus scanning and backup recovery.

Premium email service may cater to the needs of the professional business segment, which may not wish to maintain an in-house email server.

The Domain Name System (DNS) is a hierarchical decentralized naming system for computers, services, or other resources connected to the Internet or a private network.

It associates various information with domain names assigned to each of the participating entities.

Most prominently, it translates more readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols.

By providing a worldwide, distributed directory service, the Domain Name System is an essential component of the functionality of the Internet, that has been in use since 1985.

Electronic mail, or email, is a method of exchanging digital messages between people using digital devices such as computers and mobile phones.

Email first entered substantial use in the 1960s and by the mid-1970s had taken the form now recognized as email.

Email operates across computer networks, which today is primarily the Internet.

Some early email systems required the author and the recipient to both be online at the same time, in common with instant messaging.

Today's email systems are based on a store-and-forward model.

Email servers accept, forward, deliver, and store messages.

Neither the users nor their computers are required to be online simultaneously; they need to connect only briefly, typically to a mail server or a webmail interface, for as long as it takes to send or receive messages.