I can assure you that this would end up with far more problems than it will solve. I run an online store, people miss entering their email address is one of th

I can assure you that this would end up with far more problems than it will solve. I run an online store, people miss entering their email address is one of the largest causes of customers contacting support, and they regularly jump to being angry accusing us of being incompetent or worse. I would take the 0.001% of people who may have an email incompatible with a regex being frustrated (which will happen to them all the time) over the 10% who screw up entering their address. We even have code that looks for common typos and prompt the users to double check them. Somehow they still make those mistakes.