Whenever you send an email that is confrontational, emotional or otherwise uncomfortable, it can be beneficial to have a neutral person read over the content before you send it.

Since email has no inflection, by having someone who is not involved or invested in the situation read over the content, they can give you a good feel as to the tone and message you are sending. At the very least, you can gauge if you are conveying the message you want or are coming on too strong.

For this type of email, it is best to be safe before sending because you typically do not want to write based on pure emotion.