less formal, short and concise.
Don’t know the people - "Hello" is adequate.
When writing to someone you know well, feel free to write as if you are speaking to the person.
Use abbreviated verb forms (He's, We're, He'd, etc.)
Include a telephone number to the signature of the email.
Not necessary to include your email address.
When replying eliminate all the information that is not necessary. Only leave the sections of text that are related to your reply. This will save your reader time when reading your email.