EasyPG Assistant provides a minor mode
epa-mail-mode to help user compose inline OpenPGP
messages. Inline OpenPGP is a traditional style of sending
signed/encrypted emails by embedding raw OpenPGP blobs inside a
message body, not using modern MIME format.
NOTE: Inline OpenPGP is not recommended and you should consider to use PGP/MIME. See Inline OpenPGP in E-mail is bad, Mm'kay?.
Once epa-mail-mode is enabled,
the following keys are assigned. You can do it by C-u 1 M-x
epa-mail-mode or through the Customize interface. Try
M-x customize-variable epa-global-mail-mode.