This forum thread concerns the RadRichTextBox for WPF control and what Iva said in her reply is still valid - due to the low demand for this functionality (in fact, we haven't received any other requests for this) we are not considering the implementation of the feature any time soon. Actually, RadRichTextBox is more of a word processor, allowing to create, import and export flow document, so the request is a bit out of the scope of the control.
As far as the other two Telerik products that you mentioned are concerned, Telerik Data Access does not support PST files either. You could submit a feature request for this on the public Ideas & Feedback Portal of the product: Telerik Data Access
Telerik Reporting provides data source components
allowing you to retrieve data from CSV files, SQL databases or any business objects which can access the data from your PST files. Thus to use PST files to create reports, you still need a third-party library to read them.
I hope this is helpful.
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