1.Use the recipient fields correctly

 I think it is very important. If you want to sending an email to one person, place their email address in the “to” field. If you want to send the same email to others, add these addresses in the “CC:” field. Note that all the recipients will be able to see all the other recipients’ email addresses; if this is undesirable (for example, if you’re sending an email to people who don’t know each other), protect their privacy by entering each address in the “BCC:” field. This sends everyone a “blind carbon copy.” Note that for company email, use of "BCC:" may be considered impolite; addressees in the "to" field are expected to take action, and those on "CC:" are for keeping colleagues or bosses informed.