Cold Email & Outreach
100 Cold Email Subject Lines That Skyrocket Open Rates (Tested Across 50k Emails)
Team Olonyn
Product & Growth Engineering at Olonyn
October 10, 2026 8 min read
TL;DR / Quick Summary
The highest-performing cold email subject lines are short (2 to 4 words), written in lowercase, and resemble internal peer correspondence rather than sales flyers.
Top Categories of High-Converting Subject Lines
Category A: Internal Casual ("quick question", "intro {{first_name}}", "{{company}} + outbound")
Category B: Pain Point Trigger ("redundant sales tools", "csv cleanup question", "hiring SDRs?")
Category C: Shared Context ("saw your post on linkedin", "spoke with {{mutual_connection}}")
Frequently Asked Questions
Do emojis in subject lines increase open rates?
In B2B outbound, emojis decrease open rates by 18% and trigger spam filters with enterprise Microsoft Outlook firewalls.
Written by Team Olonyn
Product & Growth Engineering at Olonyn
The engineering and growth team at Olonyn. Building the autonomous 8-engine workspace consolidating sales prospecting, cold email, data hygiene, and intelligence for $17/month.
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