SharingItem.AllowWriteAccess Property (Outlook)
Returns or sets a Boolean value that indicates whether a sharing invitation should include write access to the folder. Read/write.
When sending a sharing invitation for a non-default folder, the recipient can be granted write access to the folder in addition to the default read access. This property determines if write permission should be granted to the recipient when the SharingItem is sent.
An error occurs if you attempt to set this property after the sharing message has been sent or received.