> wasting countless hours
Isn't email validation a solved problem in that there are services or ready software which provide RFC-compliant validation? If some company is wasting countless hours to do something because of Not Invented Here syndrome, isn't that the same as some company deciding to write cryptography algorithms on their own and reaping what they sow?
I'd suggest being clever is wasting countless hours to handle your edge case. Or writing your own email validation in the first place.