This is apparently a form letter science-fiction author Robert Heinlein sent back to correspondents. Created in a checklist format, the letter includes potential responses such as:
“Thanks for your kind words. You have made by day brighter.”
“You say you have enjoyed my stories for years. Why did you wait until you disliked one story before writing to me?”
and
“Please do not write to me again.”
Apparently, the last response on the list was for those who wrote the “jackpot” letters:
“Your letter was most welcome!–loaded with friendliness and with no requests or demands. You suggested that no answer was expected but I must tell you how much it pleased me. I wish you calm seas, following winds, and a happy voyage through life.”
Collect them all!