2.2.8 [RFC5545] Section 3.2.3, Calendar User Type

V0015:

The specification describes the optional CUTYPE parameter.

Microsoft Office Outlook 2007, Microsoft Outlook 2010, Microsoft Outlook 2013, Microsoft Outlook 2016, Microsoft Outlook 2019  

On export, Outlook only exports a CUTYPE parameter for the ATTENDEE property. If set, the only possible value is "RESOURCE".

On import, Outlook ignores the CUTYPE parameter on any properties other than ATTENDEE. Furthermore, values other than "RESOURCE" (case-insensitive) or "ROOM" (case-insensitive) are ignored.