A valid e-mail address is a string that matches the email
production of the following ABNF, the character set for which is Unicode. This ABNF implements the
- extensions described in RFC 1123.
email = 1*( atext / "." ) "@" label *( "." label )
-label = let-dig [ [ ldh-str ] let-dig ] ; limited to a length of 63 characters by RFC 1034 section 3.5
-atext = < as defined in RFC 5322 section 3.2.3 >
-let-dig = < as defined in RFC 1034 section 3.5 >
-ldh-str = < as defined in RFC 1034 section 3.5 >email = localpart "@" domain
+localpart = 1*( utext / "." )
+utext = ALPHA / DIGIT / "!" / ; unreserved printable ASCII
+ "#" / "$" / "%" / "&" / "'" / "*" / ; as defined in RFC5322 section 3.2.3
+ "+" / "-" / "/" / "=" / "?" / "^" /
+ "_" / "`" / "{" / "|" / "}" / "~" /
+ %80-D7FF / %E000-10FFFF ; or any non-ASCII Unicode
+domain = < a "valid host string", see URL section 3.4 >This definition supports internationalized email addresses ("SMTPUTF8"), including + non-ASCII values in both the localpart (the mailbox name or "left hand side") and domain portions + of the address. The domain must be a valid + host string. Because of the details for encoding non-ASCII domain names, it's not possible to + describe the domain portion of an address in a simple regular expression. The number and range of + Unicode characters permitted are interdependent and somewhat variable. The URL spec, + Section 3.5 describes how the domain is + validated.
This requirement is a willful violation of RFC 5322, which defines a syntax for e-mail addresses that is simultaneously too strict (before the "@" character), too vague (after the "@" character), and too lax (allowing comments, whitespace characters, and quoted strings in manners unfamiliar to most users) to be of practical use here.
-The following JavaScript- and Perl-compatible regular expression is an implementation of the - above definition.
- -/^[a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/
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-
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- A valid e-mail address list is a set of comma-separated tokens, where
each token is itself a valid e-mail address. To obtain the list of
tokens from a valid e-mail address list, an implementation must [RFC6350]