Whenever you change the status of a message in your mailbox (by changing its location, for example), a lock is placed on your mailbox so that the transfer and indexing of your messages proceeds smoothly.
Mailboxes are unlocked as soon as the procedure is complete. Normally, this happens very quickly, but occasionally the process will be interrupted and the lock will not be removed. As a safeguard in such cases, locks expire automatically after ten minutes. Simply waiting for the lock to be removed is the quickest way to deal with an inaccessible mailbox.
Please note that there may be other reasons that your mailbox might be inaccessible, in which case waiting may not solve the problem. If you continue to have trouble accessing your Inbox or another folder, please let us know.