Why I built a free email deliverability checker (and what I learned)

I built InboxGreen to solve a problem I kept seeing: developers and marketers sending emails that go straight to spam, with no idea why. SPF, DKIM and DMARC are the root cause in most cases but they're confusing to check and fix. InboxGreen makes it simple, free check for any domain, instant results, no account needed. 28 DNS tools included. Would love feedback from anyone dealing with email deliverability issues.