Don't right justify your text. Right justified monospaced text is actually harder to read on a CRT screen than plain old, ragged-right text. If you use a formatter, use a 50 column line width. Don't use lines over 80 columns and expect everybody to word wrap. Accepted jokes go into a queue that can take a month to empty.
Topical jokes go out faster.
Some replies don't make it due to bad mailers, I'm afraid. If I reply to your joke, and you want to respond, you must include a description of the joke in your response. Remember that I send out around 20 rejection notices a day, and when I get your reply back, I won't have the faintest idea which of many jokes you're talking about. Keep a short signature, with just your name and location. If you add extra, I just have to delete it.