How to Write the Perfect Subject Line

Your subject line is your first impression. Mess it up, and your email dies unopened.

This is Part 1 of our mini-series on boosting cold email open rates — what to avoid, what to copy, and how to write a subject line that has to be opened.

Avoid this

  • “SalesPort x Microsoft” / company x company — overused and template-looking
  • “Daniel from SalesPort” — too formal and impersonal
  • “For Bill: about verified contact data” — screams mass outreach

Do this instead

  • Write in all lower case — casual and approachable
  • Keep it to a maximum of 3 words — open rates tank at 4+
  • Make sure it relates to your email content — relevance wins

A/B test relentlessly

Come up with multiple subject lines and test what works for your ICP. Decide based on real data.

Target open rate: 50–90%

Short, punchy subject lines can boost open rates by up to 30%. Below 50%? Check deliverability next.

Subject line ideas

  • [Referral name] shares / endorsed / recommended
  • [Topic] tips / tactics / insights / trends
  • [Problem] solved / fixed
  • [Goal] achieved / unlocked
  • [Your company] growth / progress / proposal
  • [Product/service] upgrade / launch / release
  • [Industry] news / insights

Next up: intro lines

Make sure the first sentence doesn’t kill your email after the open.