Possible Clues:

• Write your name and position as an indicator
• Indication of what one must do before mail can be sent?
• It gives directions on how to end letters
• Indicator of direction
• Postings (anag.)
• One shows the way of putting one's name over one's letters
• Wayside indicator
• It shows one the way to finish correspondence
• Trace position, given marker
• Prepare mail for dispatch - this will give you directions