Boomerang is a plug-in that will let you know if an email goes unanswered after a certain period of time. In 2016, their customers used the plug-in's reminder feature on over 40 million emails. At the end of the year, Boomerang dug into their user data to determine what the most effective emails had in common. Here are a few of the many insights they found.
1. Lure 'em in with the subject line
David Ogilvy, regarded as the father of advertising, famously said of headlines: "On the average, five times as many people read the headline as read the body copy."
Think of your email subject line as your headline. If it doesn't catch your recipient's attention, they have no reason to open your email. And if they never open it, you're certainly not going to get a response.
Length is key. Boomerang found the shorter your subject lines, the better. "Subject lines with only 3-4 words (excluding email conventions like Re: and Fwd:) received the most responses," the company says.
During both his presidential campaigns, no one knew this sweet spot of subject line length better than Barack Obama. This graphic from New York magazine shows a snapshot of some of Obama's emails during his reelection campaign. Many of the subject lines were simply "Hey," or even "Hey again." Others included "This is critical," "Not going to happen," and "Are you in?"
Think you might catch people's attention by skipping the subject line altogether? Bad move. Boomerang found only 14 percent of (no subject) emails received a response.
2. Follow the Goldilocks rule
No one wants to open an email and be hit with a novel. The shorter the better, right? Not necessarily. Boomerang found that too-short emails were just as ineffective as too-long ones. There's a just-right length for emails that are the most likely to get a response.
"The sweet spot for email length is between 50-125 words, all of which yielded response rates above 50 percent," Boomerang says. Also consider how the person on the other end will receive your email. You might be typing it on a computer, but they could be checking emails on-the-go on their phone. Emails that appear short on a desktop screen look much longer on a palm-sized mobile screen.
Of course, no one is going to count the number of words in every single email they send. So Boomerang offers this rule of thumb for gauging length: A 50-word email is about two short paragraphs. A 125-word email is two normal-length paragraphs and one short one.
The paragraph above is just shy of 50 words.
3. Ask a question (or three)
One of the easiest ways to entice recipients to respond is to ask them a question. Boomerang found that emails containing one to three questions were 50 percent more likely to receive responses than question-less emails.
But go easy on those question marks. Going overboard with the questions is not recommended. Ask more than three, and Boomerang started to see response rates decline. If you've got a slew of questions for this person, email might not be the best channel for finding answers. Consider the old-fashioned talking on the phone method or even scheduling a face-to-face meeting.
RELATED: 19 unprofessional email habits that make everyone hate you
19 unprofessional email habits that make everyone hate you
19 unprofessional email habits that make everyone hate you
Sending 'urgent' emails that aren't urgent
"Like the boy who cried wolf, if you abuse the urgent marker, it won't be long until no one will pay any attention to it," Rosemary Haefner, chief human-resources officer for CareerBuilder, tells Business Insider.
And when you finally do send a truly urgent email, no one will pay attention, she says.
(Caiaimage/Paul Bradbury via Getty Images)
Being too casual
While the tone of your message should reflect your relationship with the recipient, Haefner says, too much informality will make you come across as unprofessional.
She advises being judicious in your use of exclamation points, emoticons, colored text, fancy fonts, and SMS shorthand.
She laments that sometimes she receives "one-line emails that are so transactional they sound like an automaton is responding."
(Just One Film via Getty Images)
"Email is not a party in the break room, it's a communication tool," Haefner says. "If you're responding to an email sent out to a group, be sure you are only hitting 'reply all' if your reply is truly necessary for everyone to receive."
(John Lund via Getty Images)
Cc'ing without approval
At the very least, sharing information that's not yours to share is annoying. It could also be a liability.
Whether you're cc'ing a client on an email where your boss said something about them or including a coworker on an email chain where another coworker shares personal information, "No one likes to have someone else decide to cc someone without being asked first," Randall says.
The best rule of thumb is to never assume it's OK to share an email with someone new to the conversation.
(Medioimages/Photodisc via Getty Images)
"I am not a big believer in blind copying people on emails," Oliver says. "When I have been bcc'd, the first thing I think is, 'If she is bcc'ing me on this, who else has she bcc'd on other emails?'"
Bcc'ing conveys distrust and secrecy, she says.
"If you need to forward an email to someone who technically should not be on the chain, cut and paste the email into a separate email for that person," Oliver suggests.
(PhotoAlto/Sigrid Olsson via Getty Images)
Using a vague subject line
"It's me," "Hey," or "FYI" give the email recipient no indication of what you're emailing them about, and they're less likely to open your email as a result.
"None of these prompt immediate attention," Randall says. "A workplace email, is best when it's clear and concise. Giving the recipient a clue can encourage them to read and reply quicker."
Starting a sentence in the subject line that you finish in the email's body
If you begin a thought or question that ends in the email, then the reader is once again forced to open the email, which is annoying, Augustine previously told Business Insider. The goal is to be clear and respectful of the recipient's time.
(Daryl Solomon via Getty Images)
A ridiculous email address
If you're sending out an email in a professional capacity, whether it's to a client, colleague, or potential employer, avoid sending it from an unprofessional email account, Randall says.
Anything cutesy, sexy, vulgar, or nonsensical will set a negative tone from the get-go. If you insist on keeping "S3xyCan1@netscape.net," at the very least create a separate email account strictly for professional emails, Randall suggests.
(Robert Daly via Getty Images)
Putting words in ALL CAPS
ARE YOU YELLING?!?! Because that's what using all caps looks like.
Unless you want to give your email recipient a heart attack, turn your CAPS LOCK off. And while you're at it, ease off on all the exclamation points.
(OZ_Media via Getty Images)
Sending too many personal emails
Jokes, touching stories, and motivational quotes sent on occasion could cheer up someone's day, Randall says, but they can quickly become tiresome.
"No matter how well-meaning you are, bombarding your coworkers' email on a daily basis can prompt them to auto-delete," she says.
(Compassionate Eye Foundation/Hiep Vu via Getty Images)
It can be tempting to show a little ire in your follow-up email, especially when you've been waiting on something that hasn't been delivered. Don't, advises Oliver.
"People always remember the mean email," Oliver says, "which is why you must not send one."
(Jupiterimages via Getty Images)
Instead, she advises writing the email you want to send, saving it in your drafts folder for 48 hours, and then revising it to take out the snippiness.
"It will help you accomplish your goal faster because you will come off as patient and professional as opposed to snarky," she says.
If you know the person really well, you can sometimes dispense with the niceties, Oliver says.
"But if the person to whom you're writing is a business colleague or a client, err on the side of politeness. Use words like 'please,' 'thank you,' and sign off with a word like, 'Best,'" she says.
(Stephan Hoeck via Getty Images)
"Sent from my iPhone," is no excuse for sloppy emails.
While Oliver says one typo here and there is becoming more acceptable because everyone is sending emails from their phones, more than one per email is unprofessional.
If the email is important enough to send out while you're on the run, it's important enough to look over before you send it out.
(Hemera Technologies via Getty Images)
Sending emails at 3 a.m.
Oliver says that she's done it occasionally herself "because sometimes you wake up very early and you're feeling productive."
But she cautions that even in this 24/7 world, "most people look at the time stamp and hold it against you if it shows some crazy hour in the morning. At best, they think you're a workaholic who doesn't have a life. At worst, they think you're obsessive."
If inspiration strikes you at odd hours of the night, Oliver suggests writing the email, saving it in your drafts folder, and sending it during working hours.
"People sometimes get carried away and put a number of exclamation points at the end of their sentences. The result can appear too emotional or immature," she writes in her book. "Exclamation points should be used sparingly in writing."
(Zoonar RF via Getty Images)
Purple Comic Sans has a time and a place — maybe? — but for business correspondence keep your fonts, colors, and sizes classic.
The cardinal rule: Your emails should be easy for other people to read.
"Generally, it is best to use 10- or 12-point type and an easy-to-read font such as Arial, Calibri, or Times New Roman," Pachter advises.
As for color, black is the safest choice.
(Charles Falco via Getty Images)
Going too long
Most people spend seconds — not minutes or hours — reading an email, and a lot of people only skim them, so write your email accordingly.
Large blocks of text are hard to read, so it's better to break emails into short paragraphs, Haefner says. Bullet points or numbered lists are even easier to digest.
(Tim Shaffer / Reuters)
You can also use bold or italics to highlight important parts of your message, but you should do so sparingly.