Be cautious about the contents of your e-mail. Many federal agencies will request e-mails as a part of their investigation. No one likes junk or unsolicited e-mail . Mail should only be sent to those people who are affected by the message. In addition, group mailings tie up the network.
Chain letters are an example of inappropriate mail.
If it is not necessary to send a group mailing, don't. If in doubt, ask your supervisor. E-mail is a district service provided by public funds. It may not be used to promote organizations outside of the school nor may it be used for an individual's personal or political agenda. Remember to exit and sign off the system.