Think very carefully about what you are trying to convey both explicitly and implicitly. Think about ways your message could possibly be mis-read. Consider the culture and customs of all parties. Think again before you forward an email message. You will never regret having asked for and received permission to forward an email in advance of doing so.
Flame wars occur when people start flaming other people.
The use of ALL CAPS is considered shouting. Shouting or yelling is rude. To send and receive email you must have client software that can operate on the Internet. The software which comes with Netscape Navigator, Microsoft Internet Explorer, or America Online should be sufficient for the casual user. If you are a high-volume email user, you would probably benefit from a dedicated email software.