a #GMimeObject to encrypt
a #GMimeEncryptFlags
an array of recipients to encrypt to
a new #GMimeApplicationPkcs7Mime object on success or null on fail. If encrypting fails, an exception will be set on err to provide information as to why the failure occurred.
Attempts to encrypt the entity MIME part to the public keys of recipients using S/MIME. If successful, a new application/pkcs7-mime object is returned.