Regulärer Ausdruck (Muster) für Email-Adresse laut W3C
"The following JavaScript- and Perl-compatible regular expression is an implementation of the above definition."
/^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/https://www.w3.org/TR/2014/REC-html5-20141028/forms.html#e-mail-state-%28type=email%29