Parse one Authentication-Results header value into its authserv-id and dkim= clauses (a header can carry more than one signature result, e.g. one per signing domain).
Authentication-Results
dkim=
One Authentication-Results header value.
The authserv-id (the first ;-separated token, '' when the value is empty) and every dkim= clause, in header order.
;
''
Parse one
Authentication-Resultsheader value into its authserv-id anddkim=clauses (a header can carry more than one signature result, e.g. one per signing domain).