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Guide · Cold email

Cold email subject lines that get opened

The short answer

The best cold email subject lines are short, specific to the reader and honest about what's inside. Three to six words, lowercase-friendly, no clickbait: the subject's only job is to make the right person open the email.

Updated 6 Oct 2026 Facts link to their sources

What makes a subject line work

  • Short. Three to six words, readable at a glance on a phone.
  • Specific. Their company or situation beats a generic benefit.
  • Plain. It should look like an email from a colleague, not a newsletter.
  • Honest. The body has to deliver what the subject promises.

Mistakes to avoid

  • Fake "Re:" or "Fwd:" on a first email. It's a trick, and readers notice.
  • Misleading subjects. In the US, CAN-SPAM requires that the subject line accurately reflect the content of the message.[1]
  • ALL CAPS, piles of punctuation and spammy words like "free!!!".
  • Talking about yourself: "Introducing our platform" gives no reason to open.

30 cold email subject line examples

Variables like {{company}} fill in from your lead list. Meerko sequences use the same format.

Short and specific

  • Question about {{company}}'s outbound
  • {{company}} + Meerko
  • Lists for {{company}}
  • Quick question, {{first_name}}
  • Your SDR hiring

About them, not you

  • {{company}}'s new office in Madrid
  • Your post on cold email
  • Congrats on the Series A
  • Saw you're hiring SDRs
  • {{first_name}}, about your talk

A clear reason to open

  • Idea for {{company}}'s pipeline
  • 3 leads for {{company}}
  • A shorter way to build lists
  • Cutting tool spend at {{company}}
  • Replies without a new tool

A referral or shared context

  • {{referrer}} suggested I reach out
  • Fellow {{school}} alum
  • From the GTM engineers meetup
  • We both use Clay
  • Mutual: {{referrer}}

Plain questions

  • Who owns outbound at {{company}}?
  • Worth a look?
  • Right person?
  • Still relevant for Q4?
  • Open to a 15-minute call?

Follow-ups (same thread, or a fresh line)

  • Re: Question about {{company}}'s outbound
  • One more idea
  • Closing the loop
  • Should I stop here?
  • Last note from me

How to test subject lines

Measure replies, not opens: a reply is the outcome you want. Change one thing at a time, send each version to a similar slice of your list, and keep the winner.

Pair a strong subject with a good first line and a clear ask: see the cold email templates and how to follow up.

Run this from your coding agent

Meerko finds the leads, sends the sequence from your own Gmail and stops it when someone replies. Self-host it for free or start on Meerko Cloud with 1,000 free credits.

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FAQ

How long should a cold email subject line be?

Short: three to six words is a good target, so it's readable at a glance on a phone.

Should I personalize the subject line?

When you have a real reason: their company, a recent event or a mutual contact. A name alone isn't personalization.

Can a subject line be misleading to get opens?

No. Under CAN-SPAM, the subject line must accurately reflect the content of the message, and misleading ones also cost you trust.

Related guides

Sources

  1. [1] FTC: CAN-SPAM Act: A Compliance Guide for Business