When writing a professional email, there are three things you should never do.
First, never use informal language. This includes slang, profanity, or any other type of language that would not be considered appropriate in a business setting.
Second, never use all caps. Writing in all caps is considered shouting, and it is very off-putting to the recipient.
Third, never use more than one exclamation point. Using multiple exclamation points is seen as unprofessional and can make you appear unprofessional.