+PGG is outdated PGP library used by old Gnus (<= v5.11), MH-E, etc.
+
+There is a PGG backend written using EasyPG called pgg-epg.el.
+However, EasyPG API is a superset of PGG and pgg-epg.el provides
+nothing but compatibility with PGG.
+
+*** Limitations of PGG
+
+As I noted "PGG is outdated PGP library" above, PGG has several
+limitations. For example
+
+- PGG can't handle a message signed with multiple keys.
+- PGG can't prompt a user which key is being used.
+- PGG can't create a binary PGP messages.
+- PGG doesn't provide a way to select keys per cryptographic operation.
+- PGG ignores GnuPG's trust metrics.
+
+** SEMI based MUA
+
+SEMI is the MIME library used by Wanderlust, cmail, T-gnus, etc.
+
+There is an EasyPG capable SEMI library called EMIKO-EasyPG. It can
+be downloaded from the same site of the EasyPG distribution point.
+
+* Security
+
+There are security pitfalls around Emacs. EasyPG is written with
+avoiding them.