Bug#769396: exim4-config: maildrop pipe transport should not add From_ line to message

[Edward Betts]

Package: exim4-config
Version: 4.84-3
Severity: normal
Tags: patch

The the default exim4 config adds an mbox-style From line to the top of
each message before it is piped to maildrop. 

The maildrop man page says: "maildrop does not accept an mbox-style
From_ line before the first header line."

Maildrop doesn't complain about the extra From_ line, but doesn't remove
it. This is a related bug against maildrop: https://bugs.debian.org/737383

The exim pipe transport can be configured to not add the mbox-stlye
From_ line by including 'message_prefix = ' in the transport. Here is 
a patch against the exim4-config package.

diff --git a/debian/debconf/conf.d/transport/30_exim4-config_maildrop_pipe b/debian/debconf/conf.d/transport/30_exim4-config_maildrop_pipe
index 0ba27bc..3bd8924 100644
--- a/debian/debconf/conf.d/transport/30_exim4-config_maildrop_pipe
+++ b/debian/debconf/conf.d/transport/30_exim4-config_maildrop_pipe
@@ -4,6 +4,8 @@ maildrop_pipe:
   driver = pipe
   path = "/bin:/usr/bin:/usr/local/bin"
   command = "/usr/bin/maildrop"
+  message_prefix =
+  message_suffix =
   return_path_add
   delivery_date_add
   envelope_to_add