I am delighted to accept your offer. A letter in which you confirm that you agree with all the terms and conditions of your new job and are ready to embark on it is called an acceptance letter.Which, like you said, hasn't been signed. Thank you for offering me the Software Engineer position! I was very happy to receive your call. I am excited about starting work and confirming the start date. As stated in the offer letter, I accept the starting salary of (Salary), and I understand that benefits will be made available to me after (X) days. Include a space where the potential employee can sign and date the letter to signify their acceptance.