I oversold 'excuses'. Let's say "means the original error lies elsewhere". I also wonder who the hell they're using - who ever heard of an email service that

I oversold 'excuses'. Let's say "means the original error lies elsewhere". I also wonder who the hell they're using - who ever heard of an email service that bans domains for being likely misspellings? The "it's as much a reason" I disagree with. Validating common typos will catch more errors than false positives, so you do get more users through your funnel than if you abandon it. "I don't like your nose" is a strict loss, this causes corrections to get real emails. So they'll still miss most typos, but it's a net gain compared to not doing it. Of course, again, I don't endorse any of this. Decide if you're ok with bad emails, follow through on that decision, use verification, and get a not-incompetent email service.