Be informative but general. Something like "When we last spoke, I was not in a good position to accept your offer.In this article, we'll explain how and when to write a letter of continued interest, and we'll answer all your LOCI-related questions. I accepted a job offer through an email but I have not yet signed the contract. Is it possible to back out of the job. I am writing to confirm my acceptance of your employment offer on April 20 and to tell you how delighted I am to be joining XYZ Corporation in Chicago. Just as you would write a cover letter or interview followup email, sometimes a formal written response to a job offer is expected.