Outlook's "Windows TXT previewer" only previews attachments with extension .txt. Is there a way to tell Outlook (2010) to use "Windows TXT previewer" on other type attachments?
For example, I would like to use it to preview .csv files and some other extensions that are just text.
In order to achieve your goal, you have to change some entries in the Registry. Preview HAndlers have GUIDs that are stored in the Registry. For each filetype, if there is one available, there is a preview handler.
For .csv files you need the Preview Handler from Microsoft Excel since a .csv file is Excel.