Interesting concept. You should probably add some try/except blocks around parts of it though, specifically around this area:

result, data = mail.search(None,'(NOT BODY "BEGIN PGP MESSAGE")') ids = data[0] id_list = ids.split()

There's a chance "result" will indicate a failure and/or "data" will be None, causing the access to data[0] to throw an exception.

I haven't looked into what the API returns for "result" so I can't speculate on a fix, but I'm sure it should be easily handled.