Electronic mail, commonly referred to as email, e-mail or simply mail is a method of exchanging digital messages from an author to one or more recipients.
Current mail systems are mostly client-server based. A mail server is an application that receives e-mail messages from e-mail clients, or from other mail servers. A mail server usually comprises a list of users, a storage area, a set of user definable rules, and a series of communication modules. The storage area is where received mail messages are stored for local users, and where messages in transit to another destination are temporarily stored. It usually takes the form of a 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 e-mail 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, and the communications modules are components that actually handle the transfer of messages to and from other mail servers and e-mail clients. Depending upon the requirements of the mail server, a number of different modules may be installed and used by the server.
A mail client is an application, used by users for reading, writing, sending and receiving e-mail messages. A mail client may be installed on a user's computing platform, but may additionally or alternatively be implemented as a web page accessed for example using a browser. The client usually comprises an editor, an address book, a folder collection or hierarchy in which messages may be stored, and communications modules. The address book allows users to store commonly used e-mail addresses in an easy to get at format, reducing the chance of addressing errors.
A mail system implemented within an organization usually consists of one or more mail servers, each connected to a multiplicity of clients, each client associated with a user or another entity within the organization, such as an employee, a group of employees, a resource such as a room, or the like.
In normal operation mode, a client composes a mail message addressed to one or more addressees. Zero, one or more of the addressees may be from the same organization, i.e., connected to the same mail server, and zero, one or more may be external to the organization. After composing the mail, it is being sent and distributed by the mail server to the internal addressees, if any, or to one or more external mail servers for distribution to the external addressees, if any.
Also in normal operation mode, a client receives e-mail messages from users within the organization or external to the organization. The user may view the received or sent mails, and may order them in accordance with predetermined parameters, such as receipt date and time, sender, subject, or the like.