TMDA was originally modeled after a little Perl script written by Thomas Erskine called Tagged Mail Sender (TMS) which implemented the concept of tagged addresses. After using TMS for a month, JasonMastaler was thrilled with how effective it was in reducing my spam problem, but the program was no longer being developed or maintained. I decided to rewrite the program from scratch and name the result TMDA. The first release of TMDA in April 2001 was essentially a rewrite of TMS in Python, and it grew from there.
As more people began to use TMDA, it became clear a more user-friendly interface was needed, so a challenge/response system was grafted on in July of 2001. Even though TMDA implements a number of techniques, the C/R system is generally what TMDA is known for. While C/R systems are now commonplace, TMDA was the first publically available program in widespread use to implement C/R as a primary anti-spam countermeasure.
There is more to life than qmail
The next hurdle was platform independence. Like TMS, early TMDA was strictly a qmail application. The decision was later made to add support for the other major Unix MTAs in order to expand usage and attract developers. This in turn would improve the overall quality of the software. Postfix support was added in October, Exim in November, and Sendmail and Courier in December of 2001.
The "DA" in TMDA
In 2002, the local mail delivery agent capabilities of TMDA were greatly improved, and in fact many now use it as a clearer and simpler alternative to Procmail or Maildrop in addition to the C/R system and other features.
The first major release
The 1.0-final release of TMDA was made in December of 2003; the fruits of almost three years of collaborative hacking. The primary developers for this developent cycle were JasonMastaler and TimLegant, with nods to the contributors mentioned in THANKS and many others who provided feedback, bug reports, and invaluable suggestions. The 1.0.x releases are considered stable and reliable, and in fact are in use at many sites in a production level capacity.
Tomorrow never dies
The envelope continues to be pushed in TMDA 1.1.x, a new development cycle, which will untimately lead to another stable release, TMDA 1.2. Currently TMDA 1.1.x should be considered "alpha" level software because it is evolving rapidly. Features and functionality are continually being added, reevaluated and improved, and subtle changes may appear between releases. JasonMastaler remains TMDA maintainer.