To create a form you first open a template on which to base it. You can either start with a blank form stored in a form library or open a form (such as a message) that has been already been used — sent to your mailbox or posted to a folder.
For information about form libraries, open the Microsoft Platform SDK on the Microsoft Developer Network (MSDN™) CD-ROM and see the topics "Form Libraries" in the Messaging API (MAPI) section and "About the Organization Forms Library" in the Microsoft Exchange Server section.
To open a blank form in design mode
Choose a template of an appropriate message class; see Outlook Forms and Message Classes.
To open a sent or posted form in design mode
Note that the fields in this form do not lose their values. If this is a message whose body contains text, that text remains visible in design mode.