In Evolution, peeking at the source code of an email is lacking a handy keyboard shortcut but still easy to acomplish.
View the Source of an Email Message in Evolution
To see the full source of an email in Evolution:
- Select View | Message Display | Show Email Source from the menu.
This will make Evolution display the source of the current message where previously the message body could be seen. To return to the normal display, select View | Message Display | Normal Display from the menu.

