Minor mode to hook EasyPG into Mail mode.
With a prefix argument ARG, enable the mode if ARG is positive,
and disable it otherwise. If called from Lisp, enable the mode
if ARG is omitted or nil.
(fn &optional ARG)
Non-nil if Epa-Global-Mail mode is enabled.
See the command `epa-global-mail-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `epa-global-mail-mode'.