Create a Custom tab and Groups in outlook 2003 using c#?

Question

i have try to create a addin for outlook 2003.i done to create a toolbar button and command bar button.

Now i want to create a new tab or groups in new mail Message(Compose mail) Window.

In outlook 2010 we have a ribbon xml to create a tab and groups.but

How can i achieve this in outlook 2003?

thanks