Unfortunately, they can do this:1) Anyone can send any letter, embarrasing or not, true or not, directly to another person (or tell them the same thing in person, over the phone, by email or text message, etc.). The law does not protect you from hearing things you'd rather not hear. If the letter were sent (e.g. as an email, with multiple CC's) to third parties, and if the accusation were untrue, that might be defamation; but defamation is only when an untrue factual statement, which damages your reputation, is made to third parties. It is not defamation to say it to you.2) Employment is employment at will, unless there was an employment contract guarantying you work. In the absence of a contract, your employer is under no obligation to call you back at all, or may predicate calling you back on you doing something about alleged bad hygiene.