Mailman currently runs only on GNU/Linux and any other *nix-like operating system, such as *BSD, Solaris, etc. It works on MacOS X but not on MacOS 9. It probably does not work on Windows, although it's possible you could get it running on a Cygwin system. (One developer has made a working Mailman 2.1 installation under Cygwin with Apache and Exim, but this is not recommended for production use.)

You must have the Python interpreter installed somewhere on your system. Currently (as of 2014-06-30) Python 2.4 or newer is required, with Python 2.7 being recommended. Mailman is not yet compatible with Python 3.

Most GNU/Linux systems and MacOSX come with Python pre-installed, so you just need to make sure you're running an up-to-date version. You can do this by executing the following at your shell's command line:

% python -V
Python 2.6.5
If your Python executable doesn't understand the -V option, it's definitely too old!

You must have a mail server (MTA) that you can send messages to, and a web server that supports the CGI/1.1 API. Apache makes a fine choice for web server, and MTAs such as Postfix, Exim, Sendmail, and qmail should work just fine.

You will need an ANSI C compiler to build Mailman's security wrappers. All modern versions of the GNU C compiler should work well.