Act as an email campaign strategist.
Write a referral email campaign (2 emails).

Brand: [BRAND]
Audience: existing customers
Incentive: [REFERRAL REWARD]
Goal: increase referrals

Constraints:
- Each email 120–170 words
- Friendly + clear

Output:
- Email 1: announce referral program (subject + preview + body + CTA)
- Email 2: reminder + social proof (subject + preview + body + CTA)