Might I add:
1. Remember Enron: when some of their officers' emails were subpoenaed, they just disgorged their entire email archive. IF you email it, it is in writing and subject to being flashed around the world by sore losers, or discovered by subpoena.
2. My worst habit: putting a postscript or personal question at the end of a message, essentially adding a second subject and messing up the email system.
PS:

ANSWER EMAILS. The new "no" is to ignore emails, or parts of them, instead of saying "no", or "I don't know", or "I'll get right back to you".