I'm lost, probably because I know nothing about SMTP and mail routing. If you were worried about typos where they accidentally use @gail.com instead of @gmail.

I'm lost, probably because I know nothing about SMTP and mail routing. If you were worried about typos where they accidentally use @gail.com instead of @gmail.com, why would it not accepting @gmail.com be relevant? Or are you talking about a typo in the routing config itself?