Your intention may be to send a private email to the poster and the message will inadvertently be sent to everyone on the list. Always check this before sending. A mistake like this can be very embarrassing and potentially costly. Email is easily misunderstood. By its very nature email seems informal causing quick and flippant responses.
Email takes on the form of a conversation without the vocal and facial tones.
Humor, sarcasm and innuendo therefore do not lend themselves well to this medium and should be avoided. Since email is typed, people with poor typing skills use too few words. Those with good typing skills often use too many. Usually neither group reads the email before sending. This should be considered when responding.