Mailchimp

Mailchimp is the most famous bootstrapped success story in SaaS history. Ben Chestnut and Dan Kurzius started it as a side project in 2001 while running a web design agency in Atlanta, charging companies to send email newsletters. They grew it to $800M+ ARR without taking a single dollar of outside investment — turning down acquisition offers and VC term sheets for 20 years — before selling to Intuit in 2021 for $12 billion. Mailchimp's growth engine was its free plan (up to 2,000 contacts free), which created massive top-of-funnel awareness and word of mouth. Every email sent from a free account had a "Sent with Mailchimp" footer badge — a form of viral distribution that put the brand in front of millions of email recipients. The company expanded from email into landing pages, postcards, social ads, and a CRM, becoming a full marketing platform. Ben and Dan reportedly walked away with $1 billion each — entirely self-made, with no investors to share the exit with.