This is not a hard and fast set of rules. This is an in general, how to get your point across on mailing lists. Most of these are as David Parter said:

[use common sense] make your posting easy for readers to read, and easy to follow the points your are trying to make. quote where and how it helps readers to understand.

• Line wrap at a reasonable width, about 70-80 characters
• Plain text is the prefered format for email, html/Word may look pretty, but they don't always make the transition to other mail readers very well.
• In general, quote what is relevant and put your reply under the quote.
• Top posting makes sense if you are going to respond to the entire message and not just parts of it

Some other documents published on the subject, and considered by some to be authoritative: http://nanog.org/listfaq.html#conventions http://www.dtcc.edu/cs/rfc1855.html http://www.humbug.org.au/netiquette.php