Sales email subject line: short, specific and tested against variants
The subject line decides whether your email gets opened or deleted. Here is how to write one that is short and concrete, and how to test variants without being fooled by the numbers.
Sales email subject line: what a good one looks like
A good sales email subject line is short, concrete and looks like something a colleague could have sent. Write a few words about what the recipient actually works on, avoid capital letters, exclamation marks and offers, and never promise more than the email delivers. The goal is to be opened by the right person, not by many people.
It sounds obvious. Still, many subject lines are written as if the recipient were standing in a shop and needed to be lured in.
Why newsletter tricks work worse on decision-makers
The person reading your email is rarely a private individual scrolling for fun. It is a sales director, a CEO or a head of procurement who gets email all day and sorts it in a few seconds. If the subject line looks like a campaign, it is treated like a campaign.
That is why newsletter tricks often backfire. Words like Offer, Sale and Free are poor choices for two reasons: the recipient recognizes the pattern immediately, and spam filters tend to treat them as warning signs. The same goes for lines in capital letters or with several exclamation marks.
An email that is meant to be read as a personal email also has to look like one. That means lowercase, ordinary sentence structure and no symbols. Look at your own inbox. Which emails do you open? Rarely the ones that shout.
Length: stick to what shows on a phone
Emails are often read first on a phone, where long lines get cut off. Whatever comes last in a long subject line is then not visible. Put the important part first.
There is no exact character count that applies to everyone, and tables of magic numbers tend to be overconfident. Our recommendation is simpler: write the line so that it still works if it is cut off after the first three or four words. Four to six words is usually enough. Two can work even better.
Sales email subject line: weak and better examples
The difference is easiest to see side by side. The lines below are invented examples, not results from any campaign.
| Weak subject line | Why it is weak | Better |
|---|---|---|
| SPECIAL OFFER for your company!!! | Capital letters, exclamation marks, says nothing about the recipient | Question about your sales team |
| Free consultation: book today | Sounds like a campaign, promises nothing concrete | Recruiting new salespeople |
| We help companies grow | Generic, fits anyone | How do you handle new leads? |
| Hi Anna, got a minute? | The name looks personal, but there is no topic | Your invoice flow |
Notice what the better lines have in common. They point to a topic the recipient already has on their desk. None of them sells anything. The selling belongs in the email, and only there if the recipient has a reason to keep reading.
Personalization: the name is not enough
Putting the first name in the subject line was once a way to stand out. Today an inserted name is easily read as a sign that the text is automated. The name says the email is addressed to someone, but not why.
It is more personal to mention something that relates to the recipient's business or role: an area they are responsible for, a process they probably have, a topic that belongs to their industry. That takes research, and that is the whole point. How the research looks depends on the rest of the email, and we cover it in five steps from research to request.
One warning: personal does not mean showing how much you know. If you write something that feels like surveillance ("I saw you changed jobs on Tuesday"), you get the opposite effect.
The subject line and the first sentence belong together
The subject line is the first half of a preview. The second half is the first words of the email, which many email clients show next to or below the line. If the email opens with "Hope you are well", you waste space where you should be continuing the same thought.
A simple test: read only the subject line and the first sentence, as if that were all the recipient saw. Do you understand who is writing, what it is about and why it concerns you in particular? If not, rewrite.
The subject line must also not create an impression that the email then contradicts. If it says "Re: your question" when nobody has asked a question, you have lost trust before the first sentence is read. That trick costs more than it gains.
How to test sales email subject lines
This is where many go wrong. They change the subject line, see the number go up and conclude that the new one was better. Testing between variants takes a little more discipline than that.
- Change one thing at a time. Keep the email text identical and change only the subject line. Otherwise you do not know what caused the difference.
- Send to comparable groups. Split the same audience randomly into two parts. If you send variant A to CEOs and variant B to marketing directors, you are testing the audiences, not the lines.
- Send at the same time. Different weekdays and times produce differences of their own.
- Measure replies, not opens. Open statistics are unreliable, because some email clients preload content and that can be counted as an open. A subject line that gets many opens but no replies has not worked.
- Wait until you have enough data. With a few dozen recipients per variant, the difference is mostly chance. Do not make decisions on two replies against one.
Keep the test small and honest: two to three variants per audience is good enough. With a small audience, testing more variants leaves too few recipients per variant, and the temptation to send to more addresses leads toward mass mailing. We explain that difference in the piece on outbound sales and mass mailing.
Here is how we work ourselves: in our setups, several variants are written for each audience, the client approves the texts before anything is sent, and the variants are tested against each other. The point is to learn what works for that specific audience, not to follow a general rule.
If you have not yet tried cold email and wonder whether it would work at all in your market, it may be wiser to get an assessment before you spend time on variants. You can book a free 30-minute call and talk that through.
The subject line in follow-ups, and when it does not help
In a follow-up, the subject line can be even shorter, or the same as in the first email so that the reply lands in the same conversation. How many follow-ups are reasonable, and at what intervals, is covered in the article on follow-up emails.
And a caveat. The best subject line cannot save an email that never reaches the inbox. If you land in spam, nobody sees your line. Start with the reasons emails end up in spam, because technology and sender reputation come before wording.
Take your latest send and read the subject line as if you had received it yourself, on your phone. Then write two shorter alternatives that mention something the recipient actually works on, and send the three variants to one comparable group each.
Frequently asked questions
How long should a sales email subject line be?
Four to six words is usually enough, and sometimes two is better. Put the important part first, because long lines get cut off on phones.
Should I put the recipient's name in the subject line?
It is not necessary. The name can be read as a sign of automation and does not explain why you are getting in touch. Mention something about the recipient's role or business instead.
What should I measure when testing subject lines?
Measure replies, not opens. Open statistics are unreliable because some email clients preload content. Change only the subject line between variants and send them at the same time to comparable groups.