Email Subject Lines That Get Opened vs. Deleted: The Psychology Behind Why Some Work and Others Fail Spectacularly
There’s nothing quite like watching your lovingly crafted email campaign get ignored. You know the content’s great. The offer’s spot-on. The design looks polished. But if no one opens it, none of that matters.
So what separates a subject line that gets clicked from one that gets binned?
Here’s what the psychology tells us, and how to write subject lines that actually get noticed.
1. We’re wired to respond to curiosity
Humans hate not knowing the end of the story. So subject lines that spark intrigue can work wonders:
“You won’t believe what happened last week…”
“This nearly went very wrong”
“What your competitors are already doing (and you’re not)”
⚠️ But beware: don’t be vague just to be clever. If you don’t deliver on the hook, people won’t open your next one.
2. Personalisation still works, but not how you think
Yes, adding someone’s name helps. But what really matters is relevance. Subject lines that make someone feel seen and understood are more likely to be clicked.
Compare:
❌ “Big Spring Sale!”
✅ “Need a fresh look for spring, Sophie?”
If you know their habits or segment your list, even better:
✅ “Spotted: your favourite’s back in stock”
3. Urgency triggers action - but only when it’s real
Subject lines with time pressure or exclusivity still perform well, but audiences are wise to fake scarcity.
“Last chance to book your place”
“Offer ends midnight”
“One day only: free delivery”
If it’s not genuinely urgent or limited, don’t say it is. Your open rate might spike, but trust will drop.
4. Numbers and lists still win
People love structure. And we love to know what we’re in for before we click.
“5 ways to cut your marketing costs”
“3 subject line mistakes to avoid”
“7 things every website should have in 2025”
Short, scannable, clear. Perfect for the inbox.
5. Avoid these common mistakes
Here’s what usually gets your email sent straight to the bin:
ALL CAPS SUBJECT LINES
Excessive punctuation!!!!!!
Being overly salesy or vague: “You’re going to LOVE this”
Bait-and-switch tactics
Subject lines that are too long or cut off on mobile
Keep it honest. Keep it snappy. And most importantly—make it about them, not you.
Final tip: Write five versions, then pick the best
Subject lines matter more than you think. Test them, tweak them, and don’t be afraid to split test if your platform allows it.
Because if they don’t open it… well, you might as well not have sent it.
We’d love to hear your story over a virtual coffee - get in touch with us hello@the-marketingdept.co.uk ☕️