Tidepodracer
The only thing else it could be if you truly confirmed there are no other running jobs is the auto-cron. You can disable email fetch for auto-cron under Admin Panel > Emails > Settings, uncheck Fetch on auto-cron, and Save Changes.
Other than that you can disable email fetch at each individual email level by going to Admin Panel > Emails > Emails, clicking the email, going to the Remote Mailbox tab, setting the Status to Disable, and Save Changes.
Cheers.