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.

The 6 Patterns That Work

1. Trigger Reference

Reference the specific event that triggered the outreach. Works best for Email 1.

• saw the series b
• the revops hire
• re: your saastr talk
• noticed the rebrand
• the hubspot migration

Why it works: Proves this isn't a blast. The recipient knows immediately why today and why them.

Rules:

• Must reference something real and recent (last 30 days)
• Keep it vague enough to create curiosity, specific enough to prove research
• Never fabricate a trigger. If caught, the relationship is dead permanently

2. Their Problem

Name the specific problem they're likely experiencing. Works for Email 1 or Email 2.

• attribution gap?
• pipeline math not working
• outbound slowing down?
• quota gap next quarter
• sdrs ramping too slow

Why it works: Forces the recipient to self-qualify. If the problem is real, they open. If not, they ignore and save everyone time.

Rules:

• Must be a real problem for their stage, role, and motion. Not a generic pain
• One problem per subject. Never "pipeline and attribution issues"
• Questions work here. Statements work too. Pick based on confidence level: question if hypothesizing, statement if signal-backed

3. Peer Reference

Name a company they'd recognize as a peer or competitor. Works best for Email 2.

• how ramp did it
• [competitor] is doing this
• gong vs. your approach
• what lattice changed

Why it works: Competitive curiosity is the strongest open-rate driver in B2B. Nobody can resist seeing what a peer did differently.

Rules:

• The peer must be in their category, stage, or motion. A Series A startup doesn't care what Salesforce did
• Must be able to back it up in the body. Never name-drop a peer in the subject without a real proof point inside
• Don't use their direct competitor if the relationship is sensitive. Use an adjacent company in the same motion

4. Open Question

Ask a question that implies you know something about their setup. Works for Email 1 or Email 2.

• still using spreadsheets?
• manual attribution?
• outbound without intent data?
• still on legacy crm?
• running sequences blind?

Why it works: Implies a better alternative exists without pitching. Creates a gap between their current state and a possible future state.

Rules:

• The question must be specific to their stack, process, or stage. "Looking to grow?" is not a question, it's noise
• Never condescending: "still doing X the hard way?" reads as patronizing
• The implied alternative should be obvious but unstated

5. Contrarian Take

Challenge a common assumption in their space. Works best for Email 2.

• less pipeline, more revenue
• stop hiring sdrs
• outbound is a product problem
• your funnel is upside down
• intent data is a trap

Why it works: Pattern interrupt. Every other email in their inbox agrees with conventional wisdom. Disagreeing earns attention.

Rules:

• Must be a take actually held and defensible. The body must follow through on the contrarian claim
• Don't be contrarian for shock value. "Sales is dead" when you're selling a sales tool is incoherent
• Works best when the recipient has likely encountered the conventional wisdom recently (a conference, a trending post, a common vendor pitch)

6. Mutual Connection

Reference a shared person, community, or context. Works for Email 1 when the connection is real.

• from [person]
• [community] intro
• [event] follow-up
• [mutual connection] suggested this

Why it works: Borrowed trust. The recipient opens because of the relationship, not the pitch.

Rules:

• The connection must be real. Fabricating a mutual connection is career-ending
• Ask the connection for permission before using their name
• If the connection is weak (same LinkedIn group, same conference attendee list), don't claim it. Use a trigger reference instead

Subject Lines by Email Position

Email 3 Subject Lines

Breakup emails get their own rules. The subject should signal finality without drama.

Use one of these (customize lightly):

• closing the loop
• should i stop?
• last note
• timing
• one last thing

Never use:

• following up (again)
• just checking in
• did you see my last email?
• 3rd attempt

Banned Subject Line Patterns

These are saturated, tested-to-death, and actively filtered by spam and human pattern recognition.

A/B Testing Rules

• Test subject lines in batches of ≥ 100 sends per variant. Anything less is noise
• Test one variable at a time: pattern, length, or tone. Never change all three
• Measure open rate at 48 hours, not 24. Second-day opens are real
• Kill variants below 35% open rate after 200 sends. Don't wait for statistical significance on obvious losers
• Winning subject line for one ICP segment may fail for another. Always segment tests by persona

Pre-Send Checklist

Run before finalizing subject lines for any sequence:

• [ ] Every subject line is ≤ 5 words
• [ ] All lowercase. No Title Case
• [ ] No emoji, no exclamation points, no ellipsis
• [ ] No personalization tokens ({first_name}, {company})
• [ ] No company names (theirs or yours)
• [ ] Email 1 subject references a real, recent signal
• [ ] Email 2 subject uses a different pattern from Email 1
• [ ] Email 3 subject signals finality without guilt
• [ ] No banned patterns from the table above
• [ ] Each subject can be backed up by the email body. No bait-and-switch
• [ ] Subject reads like a peer wrote it, not a marketer

Anti-Pattern Check

• Could this subject line apply to 1,000 other prospects? Rewrite with a trigger or specific problem
• Does it promise something the body doesn't deliver? Cut the promise or rewrite the body
• Does it use a personalization token as a crutch? Remove the token and see if the subject still works. If not, the subject is weak
• Is it clever or cute? Cold email subjects should be plain. Cleverness signals a pitch is coming
• Would a VP open this on a Monday at 8am with 47 unread emails? If not, cut it