I’m using an IMAP account in Outlook 2010 and each time I try to send a message I get the following error (but the message still gets sent);

“The Sent Items folder is unavailable.”

I get a similar error when deleting a message;

“The Deleted Items folder is unavailable.”

This error is then followed by;

“The operation failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Outlook.”

I’ve restarted Outlook but I still get all these errors. How can I solve all these folder errors?