Guide from the Subject Line Tester
Follow-Up Email Subject Lines
Short answer: a good follow-up subject names the new thing you are bringing, in a few plain words. It does not pretend you have talked before, and it does not only say you are following up. Here is what public research supports, what is simply good practice, and a few invented examples to copy the shape of.
Name the new point, not the fact that you are following up
Belkins' research on cold email follow-ups found that a follow-up should add a new point, and that a note which only checks in is weak. The subject line is the first place the reader sees whether you added anything. “Following up” tells them you are waiting. A few words about the new idea tell them why to open.
Based on: Belkins, 2023
Keep it short and plain
Gong and 30 Minutes to President's Club (30MPC) found that cold subject lines that got opened looked like internal notes: a few words, normal capital letters, and a real priority for the reader. Gong's cold email research adds that buzzwords and hype in a subject do not help. The same habits apply to a follow-up, because the reader still does not know you well.
Based on: Gong / 30MPC, 2025Gong, 2025
Four weak and better pairs
Every example here is invented to show a pattern. The names and companies are made up.
Following up versus a new point
Weak: Following up
Better: Another idea on onboarding speed
The weak version only says you are waiting. The better one tells the reader there is something new inside, about a topic they already know.
Based on: Belkins, 2023
Guilt versus help
Weak: Did you get my last email?
Better: Checklist for new support hires
The weak version asks the reader to feel bad. The better one offers something useful they can use even if they never reply.
Based on: Belkins, 2023
Shouting versus calm
Weak: URGENT: FOLLOWING UP AGAIN
Better: Question about your returns queue
All capital letters read like yelling, and fake urgency costs trust. A calm subject that names the topic feels like a note from a person.
Based on: Boomerang, 2017
A fake reply versus an honest subject
Weak: Re: our call
Better: Your team's hiring plans
Adding “Re:” when you never spoke pretends a conversation happened. Readers notice. Name the real reason you are writing instead.
Writing practice, not a study result.
Reply in the same thread, or start fresh?
If your follow-up builds directly on your first email, replying in the same thread keeps the context in one place, and the subject stays the same. If you are bringing a different idea, a fresh email with a fresh subject that names that idea is often clearer. Either way, the body has to add something. This is a writing practice, not a study result.
Writing practice, not a study result.
After a real conversation
Once you have actually spoken, a follow-up subject can name the next step you agreed on, like a document you promised or the date of the next meeting. At that point a specific next step is the better ask, and the subject can say so plainly.
Based on: Gong Labs, 2020
A quick checklist
- Names the new point or the agreed next step.
- A few words, in normal capital letters.
- No “Re:” unless it really is a reply.
- No guilt, no fake urgency, no hype.
Writing practice, not a study result.
Check the whole follow-up, too
A good subject only helps if the email behind it adds something. For the body, the free Follow-Up Email Checker at salescoachingfree.com/tools/follow-up-email-checker looks at whether your note brings a new point, skips guilt-trip phrases, and makes one easy ask.
Writing practice, not a study result.
Test your follow-up subject line
Type your follow-up subject line into the Subject Line Tester. It checks length, the inbox line, tone, and clarity, explains each point in plain words, and links the research behind it. It is free, and nothing you type is stored.
Try the Subject Line TesterSources
- Belkins. 2023 cold B2B email statistics and benchmarks (2023). Read the source
- Gong / 30MPC. 4 Data-Backed Subject Lines to Get Your Cold Emails Opened (2025). Read the source
- Gong. Does cold email even work any more? Here's what the data says (2025). Read the source
- Boomerang. The One Thing You Should Never Do In An Email Subject (Based on Data) (2017). Read the source
- Gong Labs. This surprising cold email CTA will help you book a lot more meetings (2020). 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.