Extract and validate the email address from one address segment
(Name <email> or a bare email). Text inside a quoted display name
is never taken as the address, so "Alias <a@x.com>" <b@x.com> is
b@x.com; a segment with more than one angle address is ambiguous.
Extract and validate the email address from one address segment (
Name <email>or a bareemail). Text inside a quoted display name is never taken as the address, so"Alias <a@x.com>" <b@x.com>isb@x.com; a segment with more than one angle address is ambiguous.