188.8.131.52.3 PidTagRetentionPeriod Property
The PidTagRetentionPeriod property ([MS-OXPROPS] section 2.930) specifies the number of days that a Message object can be retained. The PidTagRetentionPeriod property can be present on both Message objects and folders and can be set by both client and server.
The presence of the PidTagRetentionPeriod property on a Message object indicates that the retention tag on that Message object was explicitly applied by the end user. If the value of the PidTagRetentionPeriod property is 0, the Message object never expires.
When the PidTagRetentionPeriod property is present on a folder, it has no special significance; it simply specifies the retention period that corresponds to the retention tag on that folder.