It has been a long time coming. I used to work on a similar concept in a CRM startup about ten years ago. The project turned out quite bad because I did know about email protocols but not much about email providers and interoperability issues, so the project was later scrapped and replaced with an external service.

After many years I saw that the problem still exists - it is hard to integrate services with customers' mailboxes unless it's something straightforward like triggering a Zap for an incoming email. So, equipped with all the experience I'd gained during these years, I decided to tackle that issue again, this time under my own company.

I have made no targeted sales, and I never was in touch with the first paying customers. The only companies I discussed EmailEngine on my initiative are running it for free to this day, so these don't count as customers.

EmailEngine was first a free open source project, it gained quite a following on Github, and once I started charging for it, some of the users converted to have a paid subscription to get the upgrades.