The PROPID_M_PROV_TYPE property specifies the type of cryptographic provider used to generate the message's digital signature.
The PROPID_M_PROV_TYPE property is typically used when working with foreign queues. The type and name (PROPID_M_PROV_NAME) of the cryptographic provider is required to validate the digital signature of a message sent to a foreign queue or messages passed to MSMQ from a foreign queue. For information on sending authenticated messages to a foreign queue, see MSMQ Connector Server.
When passing PROPID_M_PROV_TYPE to MQReceiveMessage, the corresponding VT field in the aPropVar array can be set to VT_NULL.