then many S/MIME mail clients check the signers certificate's email
address matches that specified in the From: address.
-=item B<-purpose, -ignore_critical, -issuer_checks, -crl_check, -crl_check_all, -policy_check, -extended_crl, -x509_strict, -policy>
+=item B<-purpose, -ignore_critical, -issuer_checks, -crl_check, -crl_check_all, -policy_check, -extended_crl, -x509_strict, -policy -check_ss_sig>
Set various options of certificate chain verification. See
L<B<verify>|verify(1)> manual page for details.