Upper case for title of letter

Capitalise proper nouns ie Names of people or places
You could use "bold" formatting if you wish to make the heading or title stand out.
There are variouse standards for "Style" and it depends who's school of thought you follow most closely.

have a look here
http://www.io.com/~hcexres/textbook/headings.html

It sounds vaguely like it should be in all caps.

You probably want to spell "post" correctly.

Thanks, Maxdancona, for pointing out the typo.

What is your view regarding punctuation of the title?

Don't use upper case. I do think the use of quotation marks is good.

I was taught that in titles, all words other than articles, prepositions and conjunctions would be capitalized, and the first word is capitalized; nouns, pronouns, verbs, adverbs and adjectives are capitalized. So, A Tale of Two Cities, Far from the Madding Crowd, The Fall of the House of Usher. In more than 30 years of buinsess practice, though, i've never known anyone to put a title on a letter. In a memorandum, there is a subject line, and one does not follow rules of capitalization for that subject line, although some people think their material important enough to do so. I cannot think that any reasonable style manual is going to tell you to use all capitals.

Many thanks to all of you.