Real-life example: "I was upset with my boss one day and rattled off an e-mail to my coworker about how our boss should not bring stress from his home life into the workplace," says a woman from New York. "But because I was so consumed by the situation, I typed my boss's name into the 'To' line instead. Luckily, I didn't get fired. I never named him in the e-mail, and he assumed it was about someone else."

How to remove your foot: Whether your e-mail maligned a boss or a friend, own up to it immediately. Don't hastily type another note to apologize, since it could be interpreted as insincere, and become further fodder in forwarded e-mails about you. Rather, call the person and say, "I cannot believe I just did that. I am a complete idiot. I'm so sorry." If you were expressing genuine frustration in your e-mail, as opposed to general cattiness, author Caroline Tiger recommends gently addressing it: "In some situations, this faux pas could offer a starting point for discussion." Take note: The "unsend" feature offered on e-mail programs like AOL (which is owned by Real Simple's parent company, AOL Time Warner) may seem like a foot-in-mouther's fantasy, but it works only in specific cases. The recipient must use the same service provider as you do (which is often the case at the office) and must have not yet opened the offending e-mail.

In the future: "The speed, anonymity, and brusqueness of on-line writing provide the perfect breeding ground for major mishaps," says Patricia T. O'Conner, coauthor of You Send Me: Getting It Right When You Write Online ($18, www.amazon.com). "The best way to deal with this kind of thing is not to let it happen in the first place. Stop and think before you click Send, especially when you're sending radioactive material."