Mailman 2.1 installation requirements
As of this writing, Mailman 2.1.9 is not compatible with Python 2.1 or Python 2.2 and Mailman can no longer be validated against them. Also, the new Sibling Lists feature in Mailman 2.1.10 uses Python sets and thus is not compatible with Python 2.3 or older. It is highly recommended that you upgrade to the latest patch release of one of the following:
For now, we recommend using Python 2.5.2.