The recipient certificate of the message.
This property specifies the certificate to use when verifying signed files and receipts as well as encrypting files to be sent. This property must be set when SecureAuthentication has been set to true, sending a file and VirtualFileSecurityLevel has been set to slEncrypted or slEncryptedAndSigned, SignedReceipt has been set to true, or a signed file is being received and the server has not included the certificate in the signature.
This field is used to set a Private Key Certificate.
Private key certificates may be loaded from the registry, from files in PKCS#12 format, or from a PEM file format.