Always check you've got the right name in the 'To' box. And make sure your email only goes to the people who need to read it. Remember that if you reply to all, then everyone will get your email. Does the whole sales team really need to read your email to one person about something unimportant?
This is important, especially if it's a work email. If you make mistakes in your email, people will think you also make mistakes in your work. So always check everything carefully. Ask a colleague to read and check it before you hit 'Send'.