10.11 Encrypt rfc822 formated mail in a pipeline

gpg-mail-tube takes RFC-822 formatted mail on stdin and turns it into a PGP/MIME encrypted mail which is then written to stdout.

The recipients must be plain mail addresses (e.g. foo@example.org) and should in general list the To and Cc addresses contained in the mail.

gpg-mail-tube understands these options:

--verbose

-v

Enable extra informational output.

--quiet

-q

Try to be as quiet as possible.

--log-file file

Write log output to file. Use socket:// to log to a socket.

--no-stderr

Suppresses all output to stderr. This is useful for callers which don’t distinguish stdout and stderr. To get diagnostics the option --log-file can be used.

--header name=value

Add the mail header "name: value" to the output.

--setenv name=value

Put the given environment string into the environment of this process and of the called gpg. This option is required if there is no other way to set the environemt.

--gpg gpgcmd

Use the specified command gpgcmd instead of gpg.

--vsd

Use the gpg from a GnuPG VS-Desktop® AppImage. The AppImage is started if it is not running. A symlink named ~/.gnupg-vsd/gnupg-vs-desktop.AppImage needs to link to the actually to be used AppImage.

--version

Print version of the program and exit.

--help

Display a brief help page and exit.

The program returns 0 on a successful encryption or a non-zero value on error. Note that on error some output might have already been written to stdout.

The following options can be used in a local transport rule of the Exim MTA which assumes that that check_local_user has been used in the router.

transport_filter = /usr/local/bin/gpg-mail-tube --setenv HOME=${home} \
                   --no-stderr -- $pipe_addresses

For a remote transport the use of size_addition and an explicit setting of the user and its home directory might be required.