Cold email subject line tester
Type a subject line to score it on the things that decide whether a cold email gets opened or ignored — and get specific suggestions. Runs in your browser.
A heuristic based on common cold email practice, not a prediction of opens or inbox placement.
What the score looks at.
Length
Phone inboxes show roughly 30 to 40 characters of a subject. Two to six words that look like a colleague wrote them usually beat a full sentence.
Personalization
Merge fields like {{firstName}} or {{company}} make a subject feel one-to-one. They are optional — a specific, plain subject without them can work just as well.
Trigger words, capitals and punctuation
Promotional words, ALL CAPS, exclamation marks and prices make a subject look like an ad. A fake "Re:" or "Fwd:" on a first email is deceptive and costs trust.
Emoji and questions
One question can invite a reply; several look like clickbait. Emoji read as marketing in most B2B cold email.
Good subject, now the rest of the sequence.
Outly writes the email and its follow-ups with AI in your voice, threads the follow-ups in the same conversation, and stops them when someone replies.
250 leads free. No card to start.