Write an Upgrade Email Sequence

Write a 3-email upgrade sequence for free-to-paid conversion.

Context:
- Product: [WHAT IT IS]
- Free plan limitations: [WHAT FREE USERS CANNOT DO]
- Paid plan benefits: [KEY UPGRADES]
- Price: [COST OF PAID PLAN]
- Trigger for this sequence: [FREE TRIAL ENDING / USAGE LIMIT HIT / TIME-BASED]

Email 1 — Feature discovery (sent during trial/free period)
- Show them a paid feature they haven't used yet
- No hard sell — curiosity-led

Email 2 — Value milestone (sent at natural usage moment)
- Acknowledge what they have done with the free plan
- Show what's possible with the paid plan

Email 3 — Conversion push (sent as trial/limit approaches)
- Clear offer, clear CTA, urgency without pressure

For each: subject line, preview text, email body (120-150 words), CTA button text.