Harry's, a men's grooming brand, gathered nearly 100,000 email addresses in one week through the use of a simple referral mechanism. More on the brand #coming_soon. [1]

The method and means was chronicled on Tim Ferriss's blog and included the email templates, open-source code, and insider tricks—enabling readers to replicate their success. [2]

References

Harrys, harrys.com
How to Gather 100,000 Emails in One Week, tim.blog