Cold email in 2026: what indie hackers got wrong (with a Python validator I built to enforce the new rules)

If you've been sending B2B cold emails the same way for 18 months, your reply rate just dropped to ~0% and you don't know why. I rebuilt my outreach this week after my reply rate tanked from 4% to <1%. Pulled fresh data from 5+ deliverability blogs (Autobound, MarketingProfs, HyperGen, Instantly), b