After you have cancelled Sanebox, your emails stay exactly where they are. New emails will again be delivered to your inbox unless you have set up any filters in Webmail that tell otherwise.
The folders that were created by Sanebox can be deleted or renamed. The emails in the other folders, you can move to other locations.
Can I reactivate Sanebox?
If you regret your decision to cancel Sanebox, you can always reactivate it again, from Webmail or Mail Administration in the control panel. However, the free trial period of 14 days can only be used once, per email account.