HTML5: valid e-mail address

A valid e-mail address is a string that matches the ABNF production 1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section 3.5.

RFC 5322: Internet Message Format

atext = ALPHA / DIGIT /    ; Printable US-ASCII characters not including specials.  Used for atoms.
"!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{" /"|" / "}" /"~"

RFC 1034: Domain Names – Concepts and Facilities

<ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>
<let-dig-hyp> ::= <let-dig> | "-"
<let-dig> ::= <letter> | <digit>
<letter> ::= any one of the 52 alphabetic characters A through Z in upper case and a through z in lower case
<digit> ::= any one of the ten digits 0 through 9

I18n issues