2.2.3.5 PidTagExpiryNumber Property
Type: PtypInteger32 ([MS-OXCDATA] section 2.11.1)
The PidTagExpiryNumber property ([MS-OXPROPS] section 2.689) is used with the PidTagExpiryUnits property (section 2.2.3.6) to define the expiry send time. If this property is present, the value is set between 0x00000000 and 0x000003E7 (0 and 999).