Outlook 2007 “delete” grayed out

I got an user that when he tries to delete a mail message from his outlook 2007, the delete option is grayed out. But whenever he tried to delete two or more mail messages the delete option is available.

I have recreated his outlook profile but with no success.

We have just migrate this user from an imap mail server to Exchange 2010.

Any help is more than welcome, thank you!