What are the advantages and disadvantages of an email program (such as Eudora or Outlook) that automatically applies and removes protection to email messages between sender and receiver?

What will be an ideal response?

The
protection
is
automatic,
that
is,
it
is
always
applied.
But
the
protection
is
under
control
of
the
package,
not
the
user.
And
there
is
no
way
to
tell
whether
the
intended
recipient
supplied
the
key
or
it
was
retained
by
the
mail
handler.
Also,
there
is
no
way
to
avoid
the
overhead.