The QUEUE_FORMAT_TYPE enumeration identifies the type of name format being used.

 typedef  enum __QUEUE_FORMAT_TYPE
 {
   QUEUE_FORMAT_TYPE_UNKNOWN = 0,
   QUEUE_FORMAT_TYPE_PUBLIC = 1,
   QUEUE_FORMAT_TYPE_PRIVATE = 2,
   QUEUE_FORMAT_TYPE_DIRECT = 3,
   QUEUE_FORMAT_TYPE_MACHINE = 4,
   QUEUE_FORMAT_TYPE_CONNECTOR = 5,
   QUEUE_FORMAT_TYPE_DL = 6,
   QUEUE_FORMAT_TYPE_MULTICAST = 7,
   QUEUE_FORMAT_TYPE_SUBQUEUE = 8
 } QUEUE_FORMAT_TYPE;

QUEUE_FORMAT_TYPE_UNKNOWN:  The format type is unknown.

QUEUE_FORMAT_TYPE_PUBLIC:  The QUEUE_FORMAT (section 2.2.7) structure contains a GUID (as specified in [MS-DTYP] section 2.3.4) that identifies a queue.

QUEUE_FORMAT_TYPE_PRIVATE:  The QUEUE_FORMAT (section 2.2.7) structure contains an OBJECTID structure that identifies a queue.

QUEUE_FORMAT_TYPE_DIRECT:  The QUEUE_FORMAT structure contains a direct format name string that identifies a queue.

QUEUE_FORMAT_TYPE_MACHINE:  The QUEUE_FORMAT structure contains a GUID (as specified in [MS-DTYP] section 2.3.4) that identifies a queue.

QUEUE_FORMAT_TYPE_CONNECTOR:  The QUEUE_FORMAT structure contains a GUID (as specified in [MS-DTYP] section 2.3.4) that identifies a connector queue. This is not supported by all protocols.

QUEUE_FORMAT_TYPE_DL:  The QUEUE_FORMAT structure contains a GUID (as specified in [MS-DTYP] section 2.3.4) that identifies a distribution list (DL). This is not supported by all protocols.

QUEUE_FORMAT_TYPE_MULTICAST:  The QUEUE_FORMAT structure contains a MULTICAST_ID (section 2.2.10) that identifies a multicast address. This is not supported by all protocols.

QUEUE_FORMAT_TYPE_SUBQUEUE:  The QUEUE_FORMAT structure contains a direct name string that identifies a subqueue.

Note QUEUE_FORMAT_TYPE_SUBQUEUE was introduced in MSMQ version 4.