The one I see over and over is failing to trim the email before doing validation. This is especially egregious at account creation where you want no friction. U

The one I see over and over is failing to trim the email before doing validation. This is especially egregious at account creation where you want no friction. Users enter their email with their smartphone, and it may append a space at the end. More than once, I've had a relative call me trying to figure out why $website wouldn't accept their email as valid.