On any mailing list, most members are asked to abide by general rules that are basically common sense when you're dealing with a group of people.
Usually these are "rules" such as letting a person have his/her say and if you disagree, to be pleasant about it. Offer your opinions without personally attacking the person (also known as flaming).
There are other "rules" as well, and the one I think is important is the rule of snippage! What this is, is quoting only the relevant parts of the e-mail that you are replying to.
For example, if someone asks a question and then goes on to elaborate or talk about a different thing, when replying with an answer, only quote the question itself. If you are also commenting on other parts of the e-mail, then quote those too but only quote what is necessary. This helps the users on the digest mode who receive all the e-mails of the day in one big e-mail, and it also helps those who have to pay by the minute when they download e-mail (I have seen one line answers with the previous 4 posts below sent to a list and it can take up a lot of space and time).
Also, be considerate to the other members and don't post pictures or other attachments to the list, some people can't open these attachments and it can cause problems for those who receive the digest. If you have a picture you'd like to share, then upload it to a website and post the URL - don't post the picture.
Please, if you receive an e-mail which has a warning in it, check to see if it's on any urban legends site, useless mail like that also takes up a lot of time and space. If you are unsure of the validity of a message, please check [http://urbanlegends.miningco.com/].
Thanks :)