Get cold email subject lines that earn the open.
A cold email subject line should be short, specific to the recipient, and written in plain language rather than marketing language. Three to six words is the practical target, because mobile inboxes cut off most subject lines after roughly 35 to 45 characters.
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A free cold email subject line generator for B2B sales teams and founders. Describe your email or paste it in (you can attach it too), and it returns 10 to 15 short, specific subject line options across different angles, built to get opened on mobile without tripping spam filters. Free with no signup.
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Your subject line does not appear in isolation. It appears in a list next to messages from the recipient's colleagues, their boss, and systems they actually use. Anything that looks like marketing loses by comparison, because the reader is scanning for things that belong in that list.
This is why plain, lowercase, slightly unpolished subject lines outperform capitalized promotional ones. "quick question about your on-call" reads like a person. "Transform Your Incident Response Today" reads like a campaign, and the reader has learned that campaigns can be ignored without consequence.
Mobile clients typically show around 35 to 45 characters. Desktop shows more, but you should write for the tighter constraint, since a subject line that only makes sense at full length will be truncated for a large share of recipients.
The specific observation. "3 SRE openings" works because it could only have been written to this person. Specificity is the strongest available signal that the email is not a blast.
The genuine question. "question about your on-call" sets an accurate expectation and creates a small open loop. It only works if the email actually contains a question, which is worth saying because the fastest way to lose someone is a subject line the body does not honor.
The plain topic. "your blog vs your rankings" names the subject without selling. Naming a tension the recipient already feels does more than any adjective.
Lowercase and unpunctuated. Internal email is rarely title-cased. Matching that register is a small signal that adds up, particularly against a field of competitors doing the opposite.
Fake urgency and fake familiarity. "Re:" on a first email, "Following up" when nothing preceded it, or "URGENT" on something that is not. These get short-term opens and long-term distrust, and they materially raise your spam complaint rate.
Spam trigger patterns. ALL CAPS, exclamation marks, currency symbols, "free," and "guaranteed" all increase filtering risk. Modern filters weigh many signals, but there is no reason to volunteer the obvious ones.
Describing your product. The subject line is not the place to explain what you sell. It is the place to earn three more seconds of attention.
Clickbait that the email does not pay off. A curiosity-gap subject line attached to a standard pitch converts an open into resentment. Opens are not the goal, replies are.
Give it the specific trigger you noticed about the recipient, not just their industry. The trigger is what makes a subject line unrepeatable, and unrepeatable is the whole objective.
Generate several and pick by reading them in context: imagine the line sitting between an email from their CFO and a calendar notification. The one that looks least like marketing usually wins.
Test two variants across a batch if your volume supports it, and judge by reply rate rather than open rate. Open rate is increasingly unreliable due to privacy protections that pre-load images, and it was never the metric that mattered. Once the subject line works, the cold email writer handles the body, and the cold email guide covers sequencing.