The lesson
Open a cold sponsorship email with a specific thing you like about their product, then state the audience match and a small test.
Sam Parr opens "I’ve been using Wealthfront for a year now and love it" and names the chart showing his money at age 80. One line offers ad inventory, one claims audience fit ("young, high earning, early tech adopter"), and "100k daily users" backs a "small experiment". Then "Thoughts?" and a PS apologising, with his Linkedin linked.
Don't copy the audience claim or the 100k figure. Keep the praise that only a real user would know, one line on fit, and a small trial.