Guide from the Subject Line Tester
Sales Email Subject Line Examples by Situation
The right subject line depends on where you are with the reader. Below are seven common situations, each with a weak and a better subject line and one line on why. Every example is invented to show a pattern, and none comes with a promised open rate.
How to read this page
Each “why” names the Subject Line Tester check that catches the weak version, so you can test your own line the same way. The tester reads every subject as if it were going to someone who does not know you yet, which is the strictest case. The names and companies are made up.
Writing practice, not a study result.
Seven situations, weak and better
Cold first note
Weak: Streamline your onboarding with our platform
Better: Onboarding backlog at Northline
The weak line is a pitch with sales words in it. The tester's “No hype or sales pitch” check flags it. The better line names a problem the reader already owns.
Based on: Gong, 2025Gong / 30MPC, 2025
Follow-up
Weak: Following up again!!
Better: Another idea on new hire setup
Two exclamation marks read as pushy, which the “Calm, not shouting” check notes, and the line only says you are waiting. The better one promises a new point.
Based on: Belkins, 2023
After a meeting
Weak: {{first name}}, recap from today
Better: Denver rollout: recap and next step
A leftover placeholder fails the “Honest and ready to send” check. After a real call, name the project and the step you agreed on.
Based on: Gong Labs, 2020
Referral
Weak: Re: Priya's introduction
Better: Priya suggested I write about onboarding
“Re:” on a first email pretends a thread already exists, and the “Honest and ready to send” check marks it down. Name the real person who sent you, only if they really did.
Writing practice, not a study result.
Re-engagement
Weak: ARE YOU STILL THERE?
Better: Still sorting out returns delays?
All capital letters read like yelling and fail the “Calm, not shouting” check. The better line brings back the topic they cared about.
Based on: Boomerang, 2017
Event or trigger
Weak: Congrats! You won't believe this
Better: Your support hiring in Austin
A teaser that says nothing fails the “Clear, not a vague teaser” check. The better line names the real event you noticed.
Renewal
Weak: Guaranteed savings on your renewal
Better: Renewal timing for the Denver team
“Guaranteed” is hype, and the “No hype or sales pitch” check flags it. For a current customer, lead with the work you already share, not a sales promise.
Based on: Corporate Visions, 2018Gong, 2025
What the better lines share
The first three points come from the research linked in the pairs above. The last two are writing practice.
- A few words, like a note from a colleague.
- Normal capital letters and calm punctuation.
- The reader's topic, not your product.
- Honest about what is inside and how you know them.
- Specific to this reader, so it could not be sent to anyone else.
Based on: Gong / 30MPC, 2025Gong, 2025
Match the line to the relationship
Gong's research on calls to action found that a stranger should get a small ask, while someone you are already working with can get a specific next step. Subject lines follow the same idea. A first note names a topic. A note after a meeting can name the step you agreed on.
Based on: Gong Labs, 2020
Use the pattern, not the words
Copying these lines word for word will not help, because a subject that fits anyone reads like a template. RAIN Group found that buyers rate a researched, one-to-one email above a mail merge. Start from something true about your reader, then say it in as few plain words as you can.
Based on: RAIN Group, 2017
Test your subject line for your situation
Type your subject line into the Subject Line Tester. It runs the same checks named above, explains each one in plain words, and links the research behind it. You can also compare two versions side by side. It is free, and nothing you type is stored.
Try the Subject Line TesterSources
- Gong. Does cold email even work any more? Here's what the data says (2025). Read the source
- Gong / 30MPC. 4 Data-Backed Subject Lines to Get Your Cold Emails Opened (2025). Read the source
- Belkins. 2023 cold B2B email statistics and benchmarks (2023). Read the source
- Gong Labs. This surprising cold email CTA will help you book a lot more meetings (2020). Read the source
- Boomerang. The One Thing You Should Never Do In An Email Subject (Based on Data) (2017). Read the source
- Psychological Bulletin. The psychology of curiosity: A review and reinterpretation (1994). Read the source
- Saleshandy. 15 Data-backed Cold Email Templates With Frameworks (2026). Read the source
- Corporate Visions. New Corporate Visions Research Reveals Most Effective Message for Upselling Existing Customers (2018). Read the source
- RAIN Group. Top Performance in Sales Prospecting (2017). Read the source
Advice marked as writing practice is common sense for clear email, not a study result. See where all of our guidance comes from. No statistic on this page is invented.