My suggestion is to call the interviewer and just state that you have not received the offer letter. Give a neutral, nonspecific reason.An exploding offer is when a company gives you a teeny tiny window to make a decision of whether or not to take a job offer. Generally it's 24 hours or less. To create an applicant account, go to Career Pages website and click on the Sign In tab, and then Don't have an account? Simply call up the hiring manager, explain the situation, and ask. The answer to your question, regarding whether you can back out of the Offer Letter, is likely "Yes. Send the letter directly to the office, department or individuals involved in the situation. Simply sending the letter to the ombudsman is not appropriate.