Backport to Drupal 6. This is now stable enough to have withstood a live demo at the local Drupal meetup, so I may as well release it into the wild whilst people still use D6.
The only change from the original 6.x-1.x-dev version is that the view mode now actually works.
This release includes some new functionality, which now stores the node content to make the values accessible in the email handler and also fixes a node view_mode problem: