Topal — Features
Copyright © 2001–2022  Phillip J. Brooke
Topal is a ‘glue’ program that links 
GnuPG
and 
Pine/Alpine/Re-Alpine.
It
offers facilities to encrypt, decrypt, sign and verify emails,
including inline OpenPGP, MIME/OpenPGP and S/MIME.  It can also be
used directly from the command-line.
-  Multiple inline PGP blocks can be processed in display filters.
-  Decryption and verification output can be cached to reduce the
  number of times a passphrase is entered.  This also helps when
  secret keys aren't always available, at the expense of storing
  decrypted output.  
-  MIME/OpenPGP (RFC2015/RFC3156) multipart messages can be sent
  and received.  Depending on configuration, this might involve
  procmail, using sendmail-path or patching Alpine.
-  The deprecated application/pgp content-type can be sent and received.
-  S/MIME messages can be sent and received if gpgsm is
  available.  (openssl is also used in some circumstances, but
  gpgsm is still required.)
-  Topal can be used as Alpine's sendmail-path command.
-  Topal has a remote sending mode (a server and a means of
  accessing the server) for reading email on a distant computer via
  SSH with secret keys on the local computer.
-  A range of mechanisms for selecting keys for both self and recipients.
-  There is a high level of configurability (although the
  configuration interface does not expose all of it; you might have to
  edit .topal/config).
See the documentation in topal.pdf
  for further details.