I know only one way to convert or impot CSV XSLX or other files into the PST it to import them as a single attachments. Not many people know that Outlook may store any of data inside the PST file. For example you may create archive of Excel files in a single PST file. The full process is described in this article Importing any files to Outlook PST file for files archiving s However if you want to import excel worksheet into email it is better to copy and past the content as Office products have wide integration the data may be inserted like this. If you want to import the CSV data into Outlook PST file you may use menu Import & Export and then select From other program or file thenplete the importing wizard.