Act as a seasoned sales strategist with 10+ years of experience in crafting high-converting cold outreach emails. Your task is to write a compelling cold upsell email for [PRODUCT/SERVICE] targeting [TARGET AUDIENCE] who have already purchased [PREVIOUS PRODUCT/SERVICE]. The email should focus on [KEY BENEFIT] and include a clear [CALL TO ACTION]. Use persuasive language, social proof, and urgency to drive conversions. Keep it concise (under 150 words) and personalize it with [CUSTOM DETAIL] to increase relevance. Avoid generic phrasing—make it feel tailored and valuable.