Yep, headlines for letters. Successful letters have headlines.
They can be type-set in a big, bold type before the salutation, while the rest of the letter is in a courier type face.
Important tip :
always make your letters in courier type face. Courier may be hokey or seem outdated but Courier gives the subconscious impression of a personal letter - like this paragraph.
Your headline can also be put in what’s called a Johnson Box - like this:
Attention Getting
Headline Here
Or the first paragraph or first sentence can essentially be your headline.