To edit a message, type e (vm-edit-message). The current
message is copied into a temporary buffer, and this buffer is selected
for editing. The major mode of this buffer is controlled by the
variable vm-edit-message-mode. The default is Text mode.
Use C-c ESC (vm-edit-message-end) when you have finished
editing the message. The message will be inserted into its folder,
replacing the old version of the message. If you want to quit the edit
without your edited version replacing the original, use C-c C-]
(vm-edit-message-abort), or you can just kill the edit buffer
with C-x k (kill-buffer).
If you give a prefix argument to vm-edit-message, then the
current message will be flagged unedited.
As with VM `*mail*' buffers, all VM commands can be accessed from the edit buffer through the command prefix C-c C-v.