How to write subject lines that get opened
A bad subject = an unopened email = all the research and copy work wasted. The most common mistakes: clickbait (promising what's not in the body — Gmail punishes it and kills trust), spam words (Free, Guarantee, $$$), a subject that's too long (cut off on mobile), no context (the reader doesn't know what the email is about).
Good subjects:
- SPECIFIC: 'An idea for [Topic] for [Company]' instead of 'Important information',
- PERSONALIZED: name/company/trigger ('[Company] and [trigger]' — e.g. 'Saw your new branch'),
- SHORT: 3-7 words (on mobile you see ~30 characters),
- NO SPAM WORDS: zero 'Free', 'Guarantee', '100%', '$', '!!!',
- CONSISTENT WITH THE BODY: the subject promises what's in the email — otherwise the open rate rises but the reply dies (and Gmail sees it). Testing: 2-3 subject variants per campaign (e.g. A: specific-problem, B: trigger, C: name+context), you choose after 30-50 unique sent. The rule: don't optimize open rate in isolation — the subject has to lead to a reply. AI: generates 10 subject variants with categories (specific/trigger/question), filters spam words, proposes test pairs.
Subjects for the same campaign: A: 'An idea to recover 15% of leads' (specific-outcome), B: 'Your new branch and 3 salespeople' (trigger), C: '[Company] — a pipeline follow-up' (context). After 50 sent per variant: A opens 55%, B 48%, C 30%. But replies: A 5%, B 8%, C 3%. You pick B — because it leads to a reply, not just an open.
You are a subject line specialist. Context: My campaign: [DESCRIPTION — product, trigger, problem, CTA]. Task: Generate subjects: 1. 10 variants in 3 categories: specific-outcome / trigger / question (3-4 each) 2. For each: <7 words, zero spam words 3. Mark the 3 best for an A/B test (different categories) + justification 4. A spam words list to avoid (check my subjects against it) Format: 10 subjects + 3 for testing.
Variations & alternative scenarios
Tech industry version: a subject with a technical specific.
Premium services version: a subject with the outcome and the client's name.
Practical exercise
Write 6 subjects for your campaign (2 per category: outcome/trigger/question). Pick 3 for testing. Check each for spam words and length (<7 words).