2.2.3.2 PidTagDeferredSendNumber Property
Type: PtypInteger32 ([MS-OXCDATA] section 2.11.1)
When sending a message is deferred, the PidTagDeferredSendNumber property ([MS-OXPROPS] section 2.664) SHOULD be set along with the PidTagDeferredSendUnits property (section 2.2.3.3) if the PidTagDeferredSendTime property (section 2.2.3.4) is absent. The value is set between 0x00000000 and 0x000003E7 (0 and 999).
The PidTagDeferredSendNumber property is used to compute the value of the PidTagDeferredSendTime property when the PidTagDeferredSendTime property is not present.