Blog · Email Sequencing
May 25, 2025 · 5 min read
Cold email open rates have declined across the industry as inboxes got smarter and buyers got more sceptical. The majority of that decline is attributable to subject lines. Specifically, to subject lines that signal "sales email" before the prospect has read a word.
The subject line has one job: earn the open. It is not there to explain the email, describe the product, or demonstrate value. It is there to generate enough curiosity or relevance that the prospect clicks. Everything else comes after.
Subject lines that fail tend to fall into recognisable patterns. The capability subject: "[Your product] for [Company name]" — reads like an ad, gets treated like one. The leading-question subject: "Are you struggling with X?" — too salesy, too transparent. The fake-familiar subject: "Re: our conversation" without an actual conversation — works once, destroys trust permanently when the prospect realises it.
Long subject lines are also underperformers. Most email clients show between forty and sixty characters of a subject line on mobile. Anything beyond that gets cut off. The recipient reads a fragment and makes their decision. If the fragment does not earn the open, the full subject line does not matter.
Short, specific, and curiosity-generating subject lines consistently outperform alternatives. "Question about your DACH expansion" is twelve words and earns the open because it implies that you know something specific about the prospect and have a relevant question. "Quick question" is two words and works because it implies low time cost.
Name-based personalisation in subject lines — using the prospect's first name or company name — still lifts open rates in most markets. Use it where it feels natural. "[First name] — thoughts on [specific topic]" is personal without being manipulative.
A/B test subject lines with enough volume to be statistically meaningful — at least 100 sends per variant before drawing conclusions. Test one variable at a time. Short vs. long. Question vs. statement. Named vs. unnamed. Build a picture of what your specific audience responds to rather than relying on industry benchmarks.
Track open rates but do not optimise solely for them. A subject line that generates opens but sets incorrect expectations — making the email feel like a bait and switch — will hurt reply rates even as it lifts open rates. Optimise for replies, not opens.