Since all MAPI messages are instances of forms, client applications display and interact with form objects just as they do with other message objects. Client applications that use the MAPI form interfaces can provide additional interaction with form objects. Client applications can use any special verbs defined by a form to provide users with the full range of interactions intended by the form's designer. Clients can also use any custom properties that the form server exposes to help users sort, preview, or otherwise manage forms in the client's interface.
For more information, see Handling MAPI Forms.