This caught my attention, "Thank you Papa Hemingway. By the way, Ernest Hemingway self-published his first book, Three Stories and Ten Poems, after a rejection letter and look at his success! What the author whose work was rejected, (there's that unpleasant word again), should have done is bitch and moan in private and then send a polite letter or email to the agent thanking her for taking time to read his manuscript."
The quote is taken from an article on Huff Post by Kristen Houghton: The Savvy Author: What You Really Need to Know to BeSuccessful
I just got a poetry rejection, after waiting three months, from a fabulous magazine, so I goggled "sample of thank you letter for rejection by publisher" and got the following: On Writer's Relief, Famous Author Rejection Letters: True Stories Of Unbelievable Rejections. An excellent article with lots of worthwhile comments but does not have a letter to a rejection. But in other sites, according to what I read, my rejection invites me to continue submitting work: "We do, however, look forward to reading more” that put a smile on my face. I will reply by sending a couple of more poems.