Sorry, I edited my comment and then noticed you replied already. It's working by accident since the '\S+' will match the second '@', but if you had a quoted spa

Sorry, I edited my comment and then noticed you replied already. It's working by accident since the '\S+' will match the second '@', but if you had a quoted space in the user it would not work e.g. john."\ ".doe@valid.example, but would work with john.@.doe@invalid.example which I believe the regex is author meant to be caught as invalid.