Mail-foutmelding - foutmelding in Mail

Ik krijg soms deze foutmelding bij het openen of afsluiten van Mail (en ik snap er geen drol van): 'The mailbox ~/Library/Mail/Mailboxes/Deleted Messages.mbox is currently locked by Gerton on host localhost. If you open a mailbox that already is in use, you may damage its contents.' Wat is het en wat kan ik ertegen doen?

I have the same problem. I am working with OSX on the new imac superdrive. I think it has something to do with putting the computer out without logging out. I have found that if I log out and then "zet uit" .... I don't get the message anymore. I don't know if this is the solution, but it works so far.