If you feel you really have to validate an email address without sending an email to said address, don't use a regex. Use something that's meant for parsing, l

If you feel you really have to validate an email address without sending an email to said address, don't use a regex. Use something that's meant for parsing, like LPeg (for example: https://github.com/spc476/LPeg-Parsers/blob/ee63df57826fd5ef62eac5669b444e5d7c9da6ff/email.lua#L504 https://github.com/spc476/LPeg-Parsers/blob/ee63df57826fd5ef... which handles the RFC grammar, including comments) or lex/yacc or something other than a regex.