Outlook sucks for cleaning up folders based on criteria. Search and delete doesn't work for large sets of emails (pulls only 75 messages at a time from server, delete multiple times to move to trash)
Creating a mail rule with the cleanup criteria (sender, subject, date range, or what have you). Run the rule on the folder to be cleaned up. Works great over search and delete.
The rule can be kept (rename it a cleanup rule and disable, if desired) or delete for one-time cleanups.