How about tiered validation: 1. I'll let you pass no questions asked: * gotta have that '@' sign * left of '@' sign must have greater than zero characters--

How about tiered validation: 1. I'll let you pass no questions asked: * gotta have that '@' sign * left of '@' sign must have greater than zero characters-- a-z, 0-9, dots are cool, plus whatever the rules are for international characters * right of '@' whatever the rules are for domains 2. Pay me $1.99 through stripe to continue whatever you're trying to do, every time you're trying to do it: * you've got double quotes, spaces, or other "actually, emails can contain..." bullshit in the local part of the addy