The generic structures of formal invitation letters are ....
sender, receiver, opening, conflicts, and closing
sender, receiver, opening, content (time, place, RSVP, etc.), and closing
sender, receiver, opening, re-orientation, and closing
sender, conflicts, opening, content (time, place, RSVP, etc.), and closing
sender, receiver, opening, content (time, place, RSVP, etc.), and steps