Rule 6: Check for viruses.
Rule 12: Don't forward junk mail.
Rule 13: Don't e-mail confidential information.
Viruses can breach security protocols and steal important and secure information from your computer. It is important to have all emails checked for viruses before opening. Also, junk mail can contain viruses. Sometimes junk mail begets more junk mail if it's opened so it's important to ignore all junk/spam mail.
E-mailing confidential information is a serious problem. Even if you are e-mailing within a company. E-mails are often stored, even if you think they are deleted. Certain entities must save a copy of every e-mail sent and received for seven years. Because of the freedom of information act, these e-mails are a matter of public record and can be subpoenaed if necessary. This would then release the confidential information into the public eye.
Okay, see you there then lol