Can I change the appearance of the Mailman archives?
The default appearance of the Mailman list archives can't be changed. However, advanced users can use their own software scripts to create custom archives and direct visitors to those instead.
The way to do this is to create a special address at your domain name that receives mail and processes it using a script. Most archiving programs can be set up to handle mail when run in this manner.
After creating the special address, you would subscribe the address as a list member so that it receives a copy of each posting.
Your script will then be run each time a message is posted to the list, and the script can do whatever you wish to create your custom archives.