1. Never send emails that tell people you are so busy with important things.
2. Never send emails where you deny doing something inappropriate or dishonest, if you give lots of details. Students received notices from our university committee concerning itself with academic integrity. One wrote me. I am not sure what kind of potential plagiarism she is referring to, but that is not the kind that triggered the university committee's concern. Moreover, I could have allayed her fears, but I could not write to her.
3. If you want to complain about someone, don't do it in email. Better in person, or written. Email circulates.