FWIW, I use: /^\w+\@([\da-zA-Z\-]{1,}\.){1,}[\da-zA-Z-]{2,6}$/ The main idea is that an "_" (underscore) matches on \w, but is not valid as part of a domain name. It is, however, acceptable as part of the username. I use {2,6} since the there are some tld's longer than 4 chars (.museum for example).