188.8.131.52.1.5 PidTagRuleProvider Property
Type: PtypString ([MS-OXCDATA] section 2.11.1)
Rules that are stored on folders are associated with the application that owns the rules (4) by using a rule provider string. Each client application is to only add, modify or delete rules (4) that it is responsible for.
A client can define its own rule provider string. The value of the string MUST NOT be the same as a rule provider string being used by another client that could be setting rules (4) on the same folder.<2>