The glance
A subject line gets a glance on a lock screen, not a reading. Three to five words, one fact the reader can check, nothing that smells like a list. Here is what works, what kills an open, and a free tester that scores yours in seconds.
What works
{{competitor}} numbers
One researched noun. Promises information, names something specific to the reader.
your Q4 SDR roles
A fact from their own careers page: checkable, current, impossible to fake at scale.
quick one on {{product}}
Short, specific, low-key. Works because {{product}} resolves to something real.
What kills the open
Quick question
The most-sent cold subject in the language. It signals the exact opposite of rare.
Re: our conversation
A fake reply prefix. Buys one open, then poisons every word after it.
REVOLUTIONARY AI SOLUTION!!!
Shouting plus a cliché plus exclamation marks. A spam filter's favourite meal.
Partnership opportunity for [Company] to grow revenue
Ten words the reader will never see past the lock-screen truncation, and a promise you cannot keep.
FREE · INSTANT · NOTHING STORED
Questions
Three to five words, under about 45 characters. Phone lock screens and inbox previews truncate the rest, and the truncated half is usually where people put the point. Short survives; clever gets cut mid-word.
One specific, researched fact about the reader, stated plainly. A competitor's name, a role they are hiring for, a number from their world. The subject's only job is to be worth a glance from someone who owes you nothing; specificity does that, cleverness rarely does.
Yes, from the lead file, never from memory. A resolved merge field — their company, a competitor, a number — outperforms a clever generic line. But an unresolved one produces “Hi ,” or a broken bracket, which is unrecoverable, so verify the field fills before you send.
It buys one open at the cost of everything after it. The reader knows there was no prior thread, and the moment they feel tricked, every claim in the email is also a trick. Filters recognise the pattern too. It is the single most trust-destroying thing you can put in a subject.
A specific one can. “Quick question” does not — it is generic and overused. “Your DKIM setup?” might, because it is specific and the reader can tell you did the work. The test is whether the question could only have been sent to them.
The subject earns the open; the ask earns the reply. Both live in the cold email playbook, and both are what we run for clients as a cold email agency.