With the following in mm_cfg.py:
DEFAULT_EMAIL_HOST = 'lists.macosforge.org'
DEFAULT_URL_HOST = 'lists.macosforge.org'
add_virtualhost(DEFAULT_URL_HOST, DEFAULT_EMAIL_HOST)
It appears that mail sent from Mailman incorrectly shows the domain
name of the mailing list as www.macosforge.org, not
lists.macosforge.org. Investigating...