Email Subject Lines for Work: How to Get Emails Opened and Answered

Most advice on email subject lines is written for marketers chasing open rates on newsletters. This guide is for someone writing to a colleague, a manager, a recruiter or a client, who needs one particular email opened, understood and answered. Nielsen Norman Group, the user-experience research firm, advised in a 2014 article that the essential words go at the start of a subject line, since people often read only the first few words and many email programs cut the line short.¹

A good subject line for a work email names the topic and what you need, in the first few words, so the reader can decide what to do before opening it. Five rules cover most of it:

1. Put the ask or the topic first
2. Be specific enough to stand apart and be found later
3. Add the deadline when there is one
4. Keep the key words in the first 40 or so characters
5. Change the subject when the thread changes topic

For the message under the subject line, see the guide to professional email structure and tone; this page stays on the one line the reader sees first.

What makes a good subject line for a work email

A good work subject line tells the reader what the email is about and whether it needs them, like a label on a folder. Microsoft’s Outlook guidance asks for subjects that are descriptive and action-oriented, and says that if you need action, you should state what you want in the subject line itself. Its example, “Managers: Please send your Board Retreat Dates”, names who the email is for and what they must do.²

People usually decide which email to read from what they see in the inbox, before opening anything. Jaclyn Wainer, Laura Dabbish and Robert Kraut of Carnegie Mellon University in the US studied this in a 2011 paper, first by asking people to think aloud while triaging, then in an experiment that varied how specific the subject lines were. Their results suggest that uncertainty about an email’s content draws attention to it, but that the pull weakens when the email carries strong cues about its task or personal benefit and when readers have more to deal with.³ A vague subject may win a curious glance when the inbox is quiet; on a crowded day, or beside emails that state their task, that pull fades.

A colleague’s “Quick question”, by contrast, forces the reader to open it to learn whether it is a two-minute favor or a week of work, and on a full day that is reason enough to leave it.

Leaving the subject empty, in the hope that mystery gets the email opened, does no better.

Myth

A blank or mysterious subject line makes people curious enough to open and answer.

Fact

In a 2016 study of email invitations to academics and business owners, blank subject lines did not raise overall responses over informative ones, and drew more refusals.

That study, by Natalie Sappleton and Fernando Lourenço, tested invitations to take part in research rather than work requests, and this guide draws only on its published abstract.⁴ Before sending, read your subject line on its own and ask whether a stranger could tell what you need. Checking how a message lands with its reader is a habit the broader guide to workplace communication skills builds on.

A deadline in the subject line moves an email up the queue

Among the cues a subject line can carry, a deadline has the most direct test behind it. In a 2021 field experimentfield experiment: An experiment run in a real setting, such as a workplace, shop or website, with people going about their ordinary lives, usually with random assignment. It shows how an effect plays out in practice, though often for one setting and one group at a time.Full entry in the glossary by UK researchers led by Anna Cox of University College London, emails whose subject lines asked for a fast reply were answered fastest, whatever else the subject line said.⁵

The study

Limited evidence

Urgency beat value and effort in a three-week inbox test

Forty-five people received 360 test emails each over three weeks in their own inboxes. Each subject line signaled how fast a reply was needed (within 20 minutes, 3 hours or 24 hours), and some also showed how many points the reply was worth; replying earned points toward small cash prizes. Emails that needed a reply within 20 minutes were answered in about 20 minutes on average, against about two hours for those with a 24-hour window. When there was no rush, people answered the high-value, easy emails sooner; when the window was tight, they answered quickly whatever the email was worth or however much work it took.⁵

Sixteen of the 45 people answered fewer than half of the emails and were left out of the analysis, the “deadlines” were coded symbols in a points game rather than a manager’s request, and 29 analyzed participants make a small sample. The authors’ advice to senders follows from what they saw: say how urgent the reply is, how much work it will take and how much it matters, and ask for short replies when you want quick ones.⁵

A date in the subject does two jobs. “Budget sign-off needed by Thu 3 pm” tells the reader when to act and signals a small, defined task. If the job is small, say so too: “2-minute check” or “yes/no by Fri”.

How long should an email subject line be?

Keep a work subject line short enough that the part that matters survives on a phone: about 40 characters, with the key words first. Nielsen Norman Group recommends no more than 40 characters and warns that many email programs display far fewer, with limits that vary between programs and change over time.¹

There is no single cut-off because every screen and app differs: on a laptop the subject may run across half the screen, while on a phone it shares a narrow row with the sender’s name. Outlook can also show a preview of one to three lines of each message’s text in the message list, so the first line of the body is worth spending on the request as well.⁶ Mailchimp, a marketing platform, gives a wider limit of 9 words and 60 characters, based on open rates for its customers’ marketing emails.⁷ For a work email that may be read on a phone, the tighter figure is the safer one to aim at.

1. The ask or the topic, in the first words
2. The detail that sets this email apart: the project, document or date
3. The deadline, when there is one
4. Where a small screen may cut the subject off: Nielsen Norman Group advises focusing on the first 40 characters

The US Army’s correspondence rules set a similar bar for memos: a subject of 10 words or fewer where possible.⁸ “Following up on what we discussed in last Tuesday’s call about the vendor contract renewal” puts its useful words at the end, where a phone hides them; “Vendor renewal: your OK by Fri?” keeps them in view.

Five rules for email subject lines at work

The five rules below put that evidence into practice. Rules 1 and 5 rest on Microsoft’s and Google’s guidance, rule 3 on the field experiment above and rule 4 on usability research; nobody has tested the five together.

1. Put the ask or the topic first

Start with the word the reader would search for or the thing you want: “Approval needed”, “Agenda”, “Draft for review”. Microsoft’s guidance pairs the group and the action, so readers can tell at a glance what they need to do. Short prefixes such as “FYI:” and “Action Required” do a similar job, and Microsoft names both.²

2. Be specific enough to stand apart and be found later

Name the project, document, client or date: “Q3 travel policy draft” beats “Policy”. Purdue University’s writing lab asks for a meaningful subject that makes clear what the message is about.⁹ A specific subject also helps months later, when someone searches for it.

3. Add the deadline when there is one

Put the date and, across time zones, the time and zone: “by Wed 12:00 CET”. A colleague in Singapore who gets “by end of day” from Berlin cannot tell whose day you mean. Keep the deadline honest, because in the field experiment above urgency cues pushed value and effort aside.⁵

4. Keep the key words in the first 40 or so characters

Read only the first five or six words of your subject. If they do not say what the email is about, move the important words forward and cut the rest. Greetings, “Re: Fwd:” chains and phrases such as “Just checking in about” are the usual words to drop.

5. Change the subject when the thread changes topic

When the conversation moves to a new topic, give it a new subject; the section on replies below explains why.

Subject line, last look before sending

• The first words name the ask or the topic
• A stranger could tell what this email is about
• The project, document or date is named
• A real deadline is in the subject, with a time zone if needed
• The key words fit in about 40 characters
• The subject still matches what the email now discusses

Before and after: subject lines for six common work emails

The five rules apply to every kind of work email; what changes is the detail that sets each one apart. The examples below were written for this guide, with the guidance behind each fix.

A follow-up to an unanswered email can go as a reply in the same thread, so the reader sees the history, with one short line restating what you need; timing and wording for chasers deserve their own guide.

What subject line to use when sending a resume

When you email a job application, use the subject line format the posting asks for, word for word if it gives one. If it does not, include the job title as advertised, any reference number and your name. The careers office at Northeastern Illinois University in the US says employers often use specific wording to sort applications.¹¹ Saarland University’s career center in Germany gives the same advice and adds that the attachment should be named the same way.¹² Conventions differ between countries and employers, so check what the posting asks for. The body of the email and the cover letter itself then do the persuading.

Should you change the subject line when replying?

Keep the subject when you reply on the same topic, and change it when the conversation moves to a new one. With conversation view on, Gmail groups replies into one conversation and starts a new one when the subject line changes, so an unchanged subject keeps the history together.¹⁰ Microsoft’s Outlook guidance says to change the subject when the topic of the conversation changes.²

A thread called “Office move: furniture order” that drifts into a debate about parking should be split, with a new subject such as “Office move: parking for new staff”, so each decision has its own trail. Anyone who sorts mail with email filters also gains when subjects match their content.

When you edit a subject to mark progress, keep the original words and add to them: “Q3 vendor contract: signed” tells the reader the thread is closed. Gmail may then file the edited subject as a new conversation, so later replies go there.

Marketing tests on subject lines transfer only in part

Marketing platforms publish plenty of subject-line data, and a little of it transfers to work email, but it measures whether thousands of subscribers open a newsletter. Whether one colleague acts on a request is a different question. Campaign Monitor, an email marketing company, reported in a blog post last updated in 2019 that a blog subject starting “3 steps” drew 57 percent more opens than a “How to” version of the same subject; the post gives no sample size.¹³

The company’s own case study of CoSchedule, a marketing software firm, is more cautious: numbered subject lines won three of five tests, and CoSchedule concluded they did slightly better but were not a sure thing.¹⁴

The bottom line

The subject line is the part of a work email every recipient sees, so make it do the sorting for them: the ask or topic first, a specific detail, and a real deadline when you have one, all within the first 40 or so characters. Before your next request goes out, read the subject alone on your phone and rewrite it until the first few words tell the reader what you need.