Don't send abusive messages, hate-messages, or any other messages that can be construed as harassment. If someone requests that you stop sending them messages of any kind, any further messages to that individual or account will be construed as harassment. Don't send chain letters or private messages to parties not intended by the original author. Don't send messages to large numbers of recipients. Don't use an excessively large signature.
Large signatures waste valuable resources and network bandwidth.
Don't forge messages. Don't send unsolicited advertisements via mail. Don't post off-topic messages to Usenet news. Don't post the same or similar messages to large numbers of Usenet newsgroups. Aeneas explicitly forbids the use of its Network for the impersonation or false representation of another person.