I have a gmail account and Outlook 2007 is configured to leave the messages
on the POP3 server, but to remove the messages from the server when deleted
from the "deleted items" folder.

So, I downloaded all of my email (approx 17,000 messages), deleted some
messages I don't want any more and emptied the "deleted items" folder, but
the messages are not removed from the server. I've tried it several times in
several different ways, always with the same result. I can delete the local
copy on my PC, but the server copy is never removed.