This module addresses the use case where you need to send raw XML or some other text format from Webform submissions in the message body that Drupal's default core would otherwise filter tags out of to generate plain text. It also allows override of the main mail message MIME type.
The functionality is configurable at the Webform node level under the Edit e-mail settings » E-mail template » Webform Email Raw settings, and is disabled by default.
Tested with Webform 7.x-3.x, not guarantees it will work on anything older. There are no plans to backport to D6.
Emailing raw, unfiltered (filter_xss) data from a Webform submission can be risky, so only use this module if you absolutely require this behavior and understand the risks. The ideal scenario is a machine receiving and processing the emails vs. going to an inbox that is opened by an interactive mail client.
My employer Phase2 Technology graciously supported my turning this internally developed module into a contrib module.