Cold Email Subject Lines

Subject lines decide whether the email exists. 80% of cold emails die here. The body doesn't matter if the subject reads like a marketing blast.

The bar: write subject lines that look like they came from a coworker, not a vendor.

Core Rules

≤ 5 words. Shorter = higher open rate. 2-3 words is the sweet spot. Subject lines over 5 words lose mobile real estate and signal a pitch is coming.
Lowercase everything. Title Case signals marketing automation. Peers don't capitalize subject lines.
No punctuation theatrics. No exclamation points. No ellipsis. One question mark is fine if the subject is genuinely a question.
No emoji. Ever. Not even "just one."
No company name. Including their company name signals merge-tag automation. Including your company name signals nobody asked.
No first name. {first_name}, quick question is the most ignored pattern in cold email. Personalization tokens in subjects are a negative signal now.