Definition

As the name implies an e-mail server is a hardware system that specializes in the transfer of e-mail from one device to another.

An e-mail server usually encompasses a software program known as a mail or message transfer agent (MTA) that contains the protocols and coding needed to keep domain names and IP addresses organized and accessible.

Business Applications

E-mail is now such a crucial component of modern life that it has become indispensable to businesses and virtually any other human organization.

A properly functioning e-mail system generally receives a great deal of support, both capital and operational, particularly since the rise of mobile  computing and e-mail enabled mobile devices like cell phones and PDAs.

Deployment Concerns

With the growing presence of multi-vendor and multi-platform enterprises, assuring that a single e-mail system can operate under all environments is a big challenge. OS support may not extend across Windows, Linux and Mac OS X, for example, and not all servers will support both database and filesystem storage. This doesn’t necessarily mean that mail won’t get delivered, but adds to engineering and infrastructure costs to ensure the entire enterprise has access to a common feature set.

Different e-mail systems may have varying types of authentication  features, anti-spam tools and other capabilities as well, making some organizations or parts of organizations more susceptible to disruptions than others.

Integrating disparate e-mail systems is usually one of the most difficult and time-consuming IT jobs following a merger or acquisition.

Technical details

The leading e-mail server platforms include sendmail, Microsoft Exchange Server, Postfix and Exim, although the rise of hosted e-mail services like Postini (now part of  Google) is starting to eat into that market share.

Besides the MTA, an e-mail server will usually contain subsystems like a mail exchanger to organize user addresses, a mail user agent (MUA) that provides the user interface and associated mail delivery agents (MDAs) to facilitate that actual message delivery.

E-mail servers also include a wide variety of tools to address archiving, web administration, traffic control, proxy connections, search and a host of other functions.