In 2008, I wrote a pair of articles that focused on email habits that are annoying at best and career-damaging at worst. This topic proved so popular — and I have discovered and committed so many more errors since then — I thought I would share some tips for avoiding some of the most common email mistakes.

Note: This article is also available as a PDF download.

1: Address the email only when it is ready to send

Have you ever sent an email prematurely? The best way to avoid such a mistake is to leave the addressee field blank until you are positive the note is ready for sending. That way, even if you accidentally click the Send button, nothing will happen because the software won’t know where to send it. In fact, the Send button probably will be grayed out.

If you are replying to an email, follow the same procedure. In this case, however, before starting your message, cut the recipient’s name from the addressee field (this person was the original sender) and paste it into the body of your note. Then, when are ready to send, cut that address from the body and re-paste it into the addressee field.

2: Attach any files before composing your note

How many times have you gotten an email that referenced files that you never received because the sender failed to attach them? How many times have you meant to attach a file, but forgot? Avoid this embarrassment and annoyance by attaching these files first, before you even start composing your note.

3: Tell the other person which email you used when sending

Is someone saying your email was never received? Don’t answer by simply saying, “I did send you an email.”  Be specific and spell out the user name and the domain name of the address. Even if you typed the address correctly, that address might not be the main one the other person uses. In addition, of course, you could have mistyped the address or used the wrong syntax, such as typing an underscore instead of a period between first name and last name.

Likewise, if you are planning to send someone an email in the future, tell that person which address you will use.

4: Reply to a new person from the same address that received that person’s note

Let’s say you get an email from someone for the first time, but you expect to exchange more in the future. When you reply to that person, do so from the same address to which your sender addressed his or her note.

Your sender probably is using a spam filter. Such filters often will assume that any recipient of outgoing mail from that sender is good and will whitelist that recipient address. Therefore, when you reply from that address, your sender’s spam filter will allow your reply to get through.

Suppose, however, that you reply to that sender from a different email address, perhaps because the one that received the message is your less commonly used one. The sender’s spam filter might not recognize this other address, and your note could be trapped in the spam filter’s junk/spam mailbox. For this reason, the best approach is to reply from the same address that originally received that note.

5: If you want the other person to use a different address for you, say so first

What if you really would like that person to send to an alternate email address? In this case, simply say so. However, do so via phone, or via a note from the “old” address, i.e., the one your sender originally used. If you tell the sender via an email from that new address, you run into the same potential spam filter problem.

6: Send a test message first

You may get an email address from a new client or associate who dictates the address to you verbally or you might type it in by hand from a business card. To be safe, especially if you will be sending sensitive information, send a test message first to make sure you didn’t mistype while entering the address. If the person replies with a confirmation, you know that you entered the address correctly.

7: Copy and paste the address instead of manual typing

Copying and pasting an address instead of manually typing will eliminate potential mistakes. Just be aware that the address to be copied still might be wrong, so sending a test message even in such cases still is desirable.

8: Be careful with addressee auto-complete

A friend once told me of an experience she had one summer. She had written an actual hard-copy letter to her then-boyfriend. She also had written a letter to one of her girlfriends, in which she talked about some new guy she had just met. She mailed the letters, then a few days later got a call from the girlfriend telling her she had gotten the boyfriend’s letter.

Your email program might predict the name of an addressee and complete that field for you. While convenient, this feature carries with it the risk that you will send an email to the wrong person. If you can live with the risk of what happened to my friend, at least verify the addressee name before clicking Send. If you’d prefer to eliminate the risk, go into your email program’s options menu and disable the auto-complete feature.

9: Point recipient to “subject line messages”

Some guides on email advise you put a short message solely in the subject line to save time for the recipient. Be aware, though, that doing so may cause your message to be missed. Just this morning, I emailed a client with a request that he send me a check to cover mailing expenses. I put the dollar amount right in the subject line. Twenty minutes later, he emailed me back and asked for the amount. Now, this client is a good person, and I am not criticizing him. However, like many of us, he might be conditioned to click on the inbox entry and look for information in Putting the message in the subject line is still is a good idea. However, to be safe, I would put a short line in the body that says “see subject line for message.” I know it partially defeats the purpose of using the subject line this way, but it lessens the chances of missed information.

10:  Be careful about too-large attachments

Network speeds and bandwidth have increased dramatically over time. Maybe these days a 1MB attachment would not cause the problems it would have 10 years ago. Nonetheless, be sensitive to sending attachments that are too large. You still could cause problems for your co-workers and anger the network administrator, both on your side and your recipient’s side.

Ask your help desk about any limits on file sizes. Also, make sure you have to send an actual file. For example, could you merely send a Web page address instead? If you really do need to send large files, consider an FTP service such as

Bonus tip: Check and verify Web links you send

After I typed the above Web page address, I copied it and pasted it into my Web browser to make sure I got to the right page. The same principle applies here as for email addresses: You want to make sure you didn’t mistype or use the wrong domain name extension in Web addresses. If you are giving information about the White House Web site, for example, be aware that it is Use of any other extension might lead to embarrassing results for your recipient and hence problems for you.

Additional reading

Subscribe to the Developer Insider Newsletter

From the hottest programming languages to commentary on the Linux OS, get the developer and open source news and tips you need to know. Delivered Tuesdays and Thursdays

Subscribe to the Developer Insider Newsletter

From the hottest programming languages to commentary on the Linux OS, get the developer and open source news and tips you need to know. Delivered Tuesdays and Thursdays