For each of the services we gather data for, here's a guide to getting that data:
Mailman mailing lists can be downloaded, parsed and stored in a MySQL database using MLStats.
The general idea is to point mlstats at the list archive page, and let it do the work of figuring out what to download.
We are carrying a small local patch to mlstats to ensure that it re-downloads the current month's archives and reparses them. The patch has been submitted upstream.