Although email is an informal means of communication, business etiquette still applies. Write brief, professional messages. Use business email for business purposes. Avoid sending jokes and personal emails. Never send junk mail. Spam and other unwanted emails are a source of irritation for the recipient, clogging mailboxes and costing valuable time to delete them. The same is true of lengthy attachments that take a long time to download. Be sure your messages and attachments do not contain viruses that might contaminate other computers. Use caution when opening attachments from email addresses with which you are unfamiliar so your computer is not infected with a virus. Personal or sensitive information should not be sent via email, as it may be intercepted or inadvertently read by others.