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Subject line grader

Type a cold email subject line. You get a checklist of what to fix: length, a fake "Re:", capitals, punctuation, spam-like phrases and merge tags.

What it checks

  • Length: 20 to 50 characters is our rule of thumb; over 90 is flagged.
  • A fake "Re:" or "Fwd:": a subject that pretends to be a reply or a forward.
  • Capitals: shouting, whole or in part.
  • Punctuation and symbols: repeated "!" or "?", currency signs, emoji.
  • Spam-like phrases: 67 phrases that read as spam or sales-speak, from the list on the spam word checker.
  • Merge tags: placeholders such as {{first_name}}, so one is not left unfilled.

Outlevo's automatic email check flags a subject over 90 characters, a body over 2,500 characters, more than one link and a short list of spam-like phrases.

Examples, graded

Subject lines we made up, graded by the same checklist this page runs.

Subject lineScoreFirst thing flagged
Quick question about {{company}}90Phrases that read as spam
Re: our conversation65Starts with "Re:" or "Fwd:"
ACT NOW!!! Limited time offer57Heavy punctuation
Your SDR hiring plans100Nothing flagged

Made-up subject lines. The score is for this checklist, not a prediction of opens.

Why a fake "Re:" is the one to avoid

The US FTC's CAN-SPAM compliance guide puts it plainly: "The subject line must accurately reflect the content of the message." A subject that starts with "Re:" or "Fwd:" for a conversation that never happened breaks that, and it costs trust the moment the recipient opens the email. Outlevo's email review is told to treat a fake "Re:" or "Fwd:" as deception.

Questions

Does the score predict my open rate?
No. It is a score for a checklist, out of 100. Opens depend on who you are, who you write to and whether the email lands in the inbox, none of which a subject line alone shows.
Is my subject line sent anywhere?
No. The grader runs in your browser; nothing you type leaves it.
What is a good subject line length?
There is no official number. Our rule of thumb is 20 to 50 characters, with the point first, because inboxes cut long subjects off. Over 90 is flagged outright.
Is "Re:" in a subject ever fine?
Only in a real reply. Outlevo's email review is told to treat a fake "Re:" or "Fwd:" as deception. The US FTC's CAN-SPAM guide says: "The subject line must accurately reflect the content of the message." A fake "Re:" or "Fwd:" promises a thread that does not exist.
Should I put the first name in the subject?
It is optional. One specific fact about the recipient does more than a name. If you use a merge tag, give it a fallback so a missing value never shows as raw {{first_name}}.
Where do the rules come from?
The structural checks (length, a fake "Re:", capitals, punctuation, merge tags) are ours. The spam-like phrases are the list on the spam word checker, which starts with the phrases in Outlevo's own automatic check. Outlevo's automatic email check flags a subject over 90 characters, a body over 2,500 characters, more than one link and a short list of spam-like phrases.

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