Formal

This is the style for emails between friends. The email might include personal news, funny comments etc. This style is close to speech, and has informal words and conversational expressions. Many people now choose social media rather than email to communicate with friends: with social media the style is even more informal.

Neutral

This is the style of an old-fashioned letter. Ideas are presented politely and carefully, and there is much use of fixed expressions and long words. Grammar and punctuation are important. This style is not so common, but you can find it if the subject matter is serious (for example a complaint), in emails to customers where you want to make a good impression, or in some cultures where a more formal style is expected.

Informal

This is the most common style in professional/work emails. The writer and reader are both busy, so the language is simple, clear and direct. There is often a friendly opening line. Sentences are short and there is use of contractions (I’ve for I have etc.).