A Mail Mystery

I received this letter in the mail the other day. It was in this condition inside another envelope from the postal service that said something along the lines of 'we care, so we even send you damaged mail'.

Now, I know that mistakes happen and I am not complaining about the condition of the letter per se, however could a damaged letter be more mysterious than this?

Look at what is visible on the letter, something is a secret and I am suppose to know what it is.

Furthermore, it looks as though I am to respond somehow. But to whom, to where? I do not know! This was too odd not to share.

If anyone reading this received a similar, yet in tact letter, please let me know the scoop.