Display a warning, if the outbox contains messages not created by KMail.
Display a warning, if the outbox contains messages not created by KMail.

svn path=/trunk/kdenetwork/kmail/; revision=92485

lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi