[Mailman-Users] upgrading from version 2.1.9 to latest available version

I realized today that the unsubscribe via web page feature of version 2.1.9 is not working for my list. Maybe it is a known bug or something that just doesn't work for my site due to previous upgrades.

The list is very low volume so upgrading it has not been a priority. I would like to understand how much effort is involved in upgrading from version 2.1.9 to the latest available.

I am running fedora 5 if that matters.

Thank you. Chad