I don't think I understand.
If you send an email it will open in your email client. If it has an attachment, it will open in the application associated with the type of file it is.
If you have a link to a file inside the email, and you click it, it will by default open a browser, navigate to the link, and then if the browser knows what to do with it, it will pass it on to an application associated to open the file, or will simply prompt for download.
But there really is no configuration to set that's just the default behavior.
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Ignorance is not necessarily Bliss, case in point:
Unknown has caused an Unknown Error on Unknown and must be shutdown to prevent damage to Unknown.