In cold email, the subject line is the first filter — human and machine. Too long, too salesy, or too “MARKETING,” and you lose the open or the inbox.
What tends to work
Patterns that consistently perform better in B2B cold outreach:
- Short — roughly 28–50 characters; mobile truncates hard
- Specific — company, role, or problem > vague curiosity
- Lowercase or normal case — not Title Case Spam
- No fake Re:/Fwd: — filters and humans both punish this
- Few or no exclamation marks
Examples of direction (not magic scripts):
{{company}} + outboundquick question about {{topic}}{{first_name}} — {{pain}}
Personalization tokens help when they resolve cleanly. Broken {{first_name}} in the subject is worse than no token.
What to avoid
- “Free”, “guarantee”, “act now”, “limited time”
- ALL CAPS words
- Multiple
!!! - Clickbait that does not match the body
Score drafts with the cold email subject line checker or the built-in subject line grader. Both flag length, spam vocabulary, caps, and fake reply prefixes.
Preview before you send
Gmail and Outlook truncate differently. Check how the subject and preheader read in a real layout with the email inbox preview.
Subject + body as one system
A clean subject will not save a spammy body. Run the body through the spam word checker and keep length in check with the word counter.
A simple test loop
- Write 5 subject variants
- Score each
- Preview truncation
- A/B on a small verified segment
- Promote winners
Subject lines are cheap to test and expensive to ignore.
Want sequences and infrastructure, not just subject tips? Talk about a build.