Body _ The body of the letter should be broken into paragraphs with a line space (don't use indents). Also, keep sentences succinct and paragraphs short. Don't use flowery language. Address only the points you need to put across. Brevity is the key. The body of the letter should be aligned left in both formats _ Closing, Sign_Off And Name
A resignation letter is mostly sent as an email and must be addressed to the reporting manager and the HR. It's not just an information for your boss that you intent to leave but it is also an advance intimation to superiors, and human resources so that they can find a replacement for your position.