> Anything you can send an email to that is received, as far as I am concerned. 100% this. The only acceptable hard validation is to check whether there is an

> Anything you can send an email to that is received, as far as I am concerned. 100% this. The only acceptable hard validation is to check whether there is an @ between some characters. something like `.@.` in regex. It makes sense to do sanity checking (soft validation) on client side. There is 99.9% chance that `muppet@gmial.com` is wrong, outright rejecting that is wrong, though.