Electronic mail (email) is the term given to an electronic message, usually a form of simple text message, that a user types at a computer system and is transmitted over some form of computer network to another user, who can read it.

Email once consisted of a number of proprietary email systems. Originally these email systems could only send and receive email in an office where every person was equipped with the same software. With the expansion of the Internet, some manufacturers of these proprietary email systems introduced the capability of connecting to the Internet for the transfer of messages outside of the local network. This can take the form of a software interface that converts the local messages into a recognized standard form suitable for transfer over the Internet. These systems are more common in establishments that have used email for longer than most, and are renowned for minor problems with access to global Internet email, (e.g. problems with sending or receiving attachments) however such problems are slowly disappearing.

Email has become one of the driving forces behind connecting businesses to the Internet. It offers fast, economical transfer of messages anywhere in the world. As local telephone calls are free in most parts of the US, messages destined to long-distance destinations become effectively free to send. Outside of the US, local calls tend to be chargeable, therefore the email system can reduce the telephone bill considerably.

The substantial cost-cutting associated with these facts have encouraged many businesses to invest in an implementation of email services.

Email has considerable benefits over traditional paper based memo's and postal systems:

Messages can be sent at any time across the world as easily as across the office, to a group of people or a single recipient, without the sender leaving their desk. Messages can be logged, ensuring some form of record is held, and messages are stored when the recipient is away from their desk.

The recipient can collect their mail when they want, from wherever they are. Mobile users can collect their mail whilst out visiting customers, or at other locations.

The person you are sending the message to gets it directly, without passing through any third party.

Environmentally friendly! Unless requested, email messages require no paper or resources other than storage space on a computer disk drive.

An email client is an application that is used to read, write and send email. In simple terms it is the user interface to the email system.

The client usually consists of a combination of a simple text editor, address book, filing cabinet and communications module.

The text editor allows for the creation of the message itself, and usually includes simple spell checking and formatting facilities.

The ability to allow files or documents to be attached to the message is also available. For example a diagram or schematic could be attached to an email message, offering the recipient the chance to see a project's progress, and comment on it with a reply.

The address book allows the users to store commonly used email addresses in an easy to get at format, reducing the chance of addressing errors.

The filing cabinet allows for the storage of email messages, both sent and received, and usually gives some form of search function, allowing the easy retrieval of a desired message.

The final, but most important, section of the email client is the element that deals with the actual communication of email messages to and from an email server. How this actually occurs will be described later in this FAQ.

A mail server is an application that receives email from email clients or other mail servers. It is the workhorse of the email system.

A mail server usually consists of a storage area, a set of user definable rules, a list of users and a series of communication modules.

The storage area is where mail is stored for local users, and where messages that are in transit to another destination are temporarily stored. It usually takes the form of a simple database of information.

The user defined rules determine how the mail server should react when determining the destination of a specific message, or possibly react to the sender of the message. For example: specific email addresses can be barred, or certain users can be restricted to only sending messages within the company.

The list of users is a database of user accounts that the mail server recognizes and will deal with locally.

The communications modules are the components that actually handle the transfer of messages to and from other mail servers and email clients. Depending upon the requirements of the mail server there may be a number of different modules installed for use. What these modules do and how they communicate will be dealt with later in this FAQ.

A person, sometimes called a Postmaster, maintains the mail server and the list of user accounts that it supports.

Most mail servers are designed to operate without any manual intervention during normal operation. They wait for a message to be sent to them and process it accordingly, or collect messages from other mail servers at predetermined intervals.