Short and easy to scan
Subjects that get opened tend to be a few words, like a note from a colleague.
Free sales email subject line checker
Subject Line Tester
Type your subject line. Get a plain-English grade, the reasons behind it, and the public research each check comes from.
- Free, no sign-up
- Nothing is stored
- Every rule shows its source
What the Subject Line Tester checks
Eight checks, each explained in plain words. Checks based on research link to the source. The rest are labeled as writing practice.
Fits the inbox line
Many mail apps cut the visible subject off around 60 characters. This is a writing practice, not a study result.
Writing practice
Calm, not shouting
All capital letters read like yelling.
No hype or sales pitch
Pitch words, buzzwords, and big numbers in a subject tend to work against you.
Says what it is about
A first name alone is not proof the email matters to them. The topic is.
Honest and ready to send
No fake "Re:" on a first email, and no leftover fill-in placeholders. This is a writing practice, not a study result.
Writing practice
Spelling and grammar
A typo in the subject is the first thing they see. This is a writing practice.
Writing practice
Clear, not a vague teaser
Curiosity is optional. When you use it, it should be specific, not a teaser that says nothing.
Questions
What makes a good sales email subject line?
Short, plain, and about the reader's priority. It should read like a note from a colleague, not an ad: a few words, normal case, no hype, and honest about what is inside.
How long should an email subject line be?
A few words is a good target for a sales email. Keep it under about 60 characters so most inboxes show all of it.
Does putting their first name in the subject help?
Not by itself. A 2023 replication did not find the first-name lift an earlier marketing test reported. Naming their topic or priority matters more.
Does this tester predict my open rate?
No. It checks your subject against published research and common writing practice, and explains each point. It does not promise open or reply rates.
Is the Subject Line Tester free? Do you store what I type?
It is free with no sign-up, and nothing you type is stored.
Want the whole email graded?
The Free Sales Email Grader checks the subject and the body together, against several sales methods, and suggests a rewrite.
Try the Free Sales Email Grader