Description of problem: 
Pressing RETURN when a window containing a received message has focus immediately duplicates that window.


Version-Release number of selected component (if applicable):
evolution 3.16.4

How reproducible:
Every time

Steps to Reproduce:
1. Open a previously received e-mail
2. While it has focus, press RETURN


Actual results:
The window is duplicated and given focus.

Expected results:
I expected the RETURN press to be ignored because the window can't be edited.

Additional info:
Each successive RETURN repeats the duplication and shifts focus to the new window. Seems to continue until you get bored with doing it.

This always happens and is unaffected by:
- Caret mode being on or off
- whether the cursor is on the text in the received message window window or not

A nice short cut would be for RETURN to open a Reply window and position the cursor inside it. However, this should be a configurable feature and should default to OFF.