Most of the usual Emacs commands are available in Rmail mode, though a few, such as C-M-n and C-M-h, are redefined by Rmail for other purposes. However, the Rmail buffer is normally read only, and most of the letters are redefined as Rmail commands. If you want to edit the text of a message, you must use the Rmail command e.
The e command (
rmail-edit-current-message) switches from
Rmail mode into Rmail Edit mode, another major mode which is nearly the
same as Text mode. The mode line indicates this change.
In Rmail Edit mode, letters insert themselves as usual and the Rmail commands are not available. When you are finished editing the message and are ready to go back to Rmail, type C-c C-c, which switches back to Rmail mode. Alternatively, you can return to Rmail mode but cancel all the editing that you have done, by typing C-c C-].
Entering Rmail Edit mode runs the hook
text-mode-hook; then it
runs the hook
rmail-edit-mode-hook (see section Hooks). It adds the
attribute `edited' to the message.