Sendmail – A Mail Transfer Agent

Sendmail is what is known as a Mail Transfer Agent in other words it is the gateway software that allows you to send an email from your email account out onto the web and then delivers it to the recipients email box. It is the most popular MTA in use today as it is capable of interfacing with a large number of mail transfer and delivery methods. This includes the Simple Mail Transfer Protocol that is used by most email servers around the world.

The Beginning of Sendmail

In 1979 Eric Allman wrote a program called Delivermail that shipped out with BSD 4.0 and 4.1. In the early 80s he went on to write Sendmail while at UC Berkley and it was subsequently shipped with BSD 4.1c making it the first version of BSD that include the ability to use TCP/IP protocols. While Sendmail was designed to be very flexible and utilized open source code it can still be challenging for inexperienced techs to install and maintain.

Popularity Explosion

Because it was based on free and open source code Sendmail worked very well with UNIX based servers and by 2001 Sendmail had captured some 42% of the public mail servers making it the most popular MTA on the internet. This may have been because it has long been considered the standard MTA for most of the different variations of UNIX and UNIX like operating system, which are still among the most popular operating systems for mail servers.
There are other MTAs being used and today the market share of Sendmail is reported to have dropped to less than 30%, but it is still the most common MTA in use.

Part of the loss of popularity may be in the fact that in order to configure it the technician must be able to work with M4 macro language programming, however Sendmail must be properly configured to allow email to be received and sent out properly.

Competition

As Sendmail began to decline in popularity other companies began to take up the slack, one of the biggest competitors is qmail. Qmail was written by Dan Bernstein in 1995 as an MTA to work directly within the UNIX community. He had been working with Sendmail and was determined to come up with a software package that provided far better security as the early versions of Sendmail were full of security loopholes.

As the popularity of the Internet became to bloom so did the level of unsavory people using it. The security flaws within Sendmail became unbearable and Qmail was written to fill the gaps and make email safer and faster for the users with far greater flexibility.

Sendmail the Next Generation

Sendmail continued to be developed as far as version 9 which was renamed Sendmail X as it did not use the same code base as Sendmail 8. However before it could be fully developed progress on Sendmail X was halted and a new project called MeTA1 was pushed ahead. While Sendmail is still very much in use today the last version of Sendmail X was released in May of 2006 and licensed under the same license as Sendmail 8. These recent advance in the program have addressed the security flaws and with the optional features it has become a little easier to configure.