E-mails are a staple of the business world and whether we like them or not, they are here to stay a while longer. When writing e-mails you should focus on being both efficient (no War and Peace novels, please) and effective (get your point across and go for the desired outcome). Focus on actionable items or knowledge sharing and exclude other useless information which provides no value.
When writing an e-mail address it ONLY to people that you need to ACT on something or that you believe should be INFORMED of something, no one else! Finally, include immediate supervisors ONLY if there’s no progress or acknowledgement, not as a default practice.