Correct file name extension for MIME 'text/enriched' file format?
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Emacs offers the ability to use the MIME standard `text/enriched` for writing enriched text. What is the canonical file name extension for this format. Emacs seems to think it's `.doc`, but this could be confused with the more common Microsoft Word `.doc` format. Is there an alternative?

(I know it's not `.rtf`, which is a format different from both Microsoft's `.doc` and MIME's `text/enriched` formats)