Subject Line (Cold Email)

The subject line is the gate to your cold email. No open means no read, no reply, no meeting. Yet it gets the least attention of any element in a sequence — most teams focus on body copy and neglect the 3–7 words that determine whether the email gets opened at all.

What works in cold email subject lines

Research on cold email open rates consistently points to the same principles:

Short and lower-case: Subject lines of 3–6 words, written in sentence case (not title case), consistently outperform longer, formally capitalised ones. “Quick question” outperforms “Introducing Our Lead Generation Platform.”

Personalised: A subject line that references the company name, a recent event, or a specific pain point specific to that recipient dramatically outperforms generic ones. “[Company] + [Your Company]” is a pattern that’s been beaten to death — but “[Company]‘s SDR hiring” works because it’s specific.

Curiosity-driven: Subject lines that create an information gap — where the prospect has to open to find out what you’re referring to — generate higher open rates. But curiosity that doesn’t connect to the email body destroys trust.

Avoid spam triggers: Words like “free,” “guaranteed,” “100%,” excessive punctuation (!!! or ???), and all-caps trigger spam filters and pattern-match to promotional email.

Open rate benchmarks

Good cold email open rates: 40–60%. Great: 60–75%. Above 75% typically means a very tight, well-warmed list. Below 30% indicates deliverability or relevance issues.

Related concepts

Subject lines drive open rate. Open rate is a deliverability signal as much as a copy signal. The preview text (the snippet after the subject line in most inboxes) is the second chance to earn the open.