Retrieve the signature ultimately used to verify a message.
||dkim_getsignature() is called after
dkim_eom() to get a handle referring
to the signature which will be used to yield a final result to the
||Message-specific handle, returned by
- The function was called before dkim_eom.
- The function was called with a handle that was not
opened for verification.
- The message represented by dkim was not signed.
||A handle referring to the first signature found to be valid
that was not flagged to be ignored by the caller, or if none
were valid, the first signature not flagged to be ignored by the