This week I'll first discuss when you should reply to everybody and when you should only reply to one person, then consider the problem of how much formatting in your email is too much.
Replying to Everybody
Sometimes everybody really does need to receive your reply. Other times, they really don't. This is sometimes a difficult problem to deal with: is it better to err on the side of replying to everybody (thus sending people a bunch of spam) or the side of replying to only one person (and leaving people out of the loop)? That's really a matter of personal preference, but usually you should be able to make a pretty good decision. Here are a few cases:
- If somebody asked you about a meeting or similar group activity, you should reply to everybody. Otherwise other people might not realize that you've already replied and make plans that don't work for you behind your back (like you just did to them!).
- There is very rarely a sensible reason to send an email that says something like "Thanks" or "Cool, I'll do that" to everybody. In fact, you might consider whether you really need to send that email at all—in many cases, all it will end up doing is wasting the other person's time. (Of course, there are plenty of times when being courteous is intelligent. But it's at least worth thinking about.)
- If you're on a mailing list and really only need to reply to one person, see if the mailing list allows you to see the email address of the person who sent it. If so, don't hit reply—copy that email address, then compose a new email to that person, rather than to the entire list.
- Consider choosing "reply to all," then removing several people's names from the address list. Perhaps only the person who just sent you an invitation and the person you know who just responded need to get an email, not the other three people on the original mailing as well.
- If somebody sent you an email with two hundred names in the To: field, first of all, shame on them. Second of all, please double-check to make sure you didn't hit "reply to all" before you send the email. If there's something worse than getting a completely useless email from somebody, it's getting a completely useless email from somebody you don't even know.
I know some people will say, "Big deal! It doesn't take that long to delete a useless email—why should I bother to think about all this before I send email?" But think about it this way: either you spend a few seconds thinking about who needs to get your email, or someone else spends a few seconds deleting your email because she didn't need it. If all of us were polite and spent a few seconds considering who needed to receive our emails, then we would all have fewer useless messages drifting around in our inboxes (that sometimes even interrupt our work because we notice that we have a new email and go to see what it is). And we wouldn't lose any time because of it, either—we would simply have moved those few seconds from the receiving to the sending end.
HTML and Formatting
Have you ever gotten an email that was in 18-point italic red text with a blue speckled background? I sure have. And guess what: it doesn't make you look cool. All it does is strain people's eyes, make them annoyed because it's difficult to read, and make their email take longer to load. Simply put: stick with plain text unless you actually have a good reason to add formatting.
Some people dislike getting any formatting in email (mostly the technical people who use text-based email programs, for whom any formatting displays as HTML markup and random gibberish). You'll probably know who these people are, because they'll write you back asking you to please send them plain text-only email in the future. If you're not dealing with one of those people, adding some bold text, a link, or maybe a relevant image to the body of your email looks professional and is perfectly acceptable. Changing the font of your entire email to Comic Sans, putting the entire thing in italics, or adding a background is obnoxious.