In Outlook 2003 and older, you can also use the Tools | Forms | Design this form command in an opened item. In Outlook 2007 and older, you can open forms from the Tools | Forms menu, choosing Design a Form when in the main Outlook window. If you prefer, you choose Design a Form and browse for the form type you want to design. Any content already in the Outlook item will be carried over into the form. Once you have the Developer ribbon enabled, you can open a new Outlook item (of the type you want to design) then choose Developer ribbon, Design this form and the form opens in design mode. Video Tutorial: Enable the Developer Ribbon
You can also open the Forms Designer as you would for all older versions: using Outlook's Tools, Forms menu. In Outlook 2007 you need to enable the Developer ribbon for Outlook items (mail, calendar, contact forms, etc) from the Office Icon, Editor options dialog.
