So I heard the good people in PBMS complain about how hard it is to delete messages en mass, especially the auction ones, and thought it would be a good idea to create a script that help you do this. The script can automatically delete all visible (ie. out of the 50 most recent mail) auction messages*, and also adds a small checkbox on each message allowing you to delete them in bulk. If you have more than 50 mail it'll be a good idea to reload the page to get more mail to show up.
Install | Source
If you're on Firefox, you'll need to install Greasemonkey. If you're on Chrome, you'll be prompted to download the file. Open up your extensions tab and drag the downloaded script into the tab to install it.