Many of our clients use email clients like Apple Mail, Thunderbird, Outlook, iPhone/iPad/Android, but by default Google archives any message that’s marked as deleted.
Running a GMAIL search (at http://gmail.com) for the following query allows you to mass delete (run the search, select all the messages, hit the trash button) messages that aren’t labeled (and therefore are likely to have been previously archived).
has:nouserlabels in:all -label:inbox -label:trash
Add this criteria to filter a specific date range:
This example will only select messages between January 1, 2008 and January 2, 2012.
Hope that helps.