#172 Respect --rcpt-to parameter for dspam client to daemon

[Thomas Preud'homme]

As reported in Debian [0], "--rcpt-to ${recipient}" doesn't work as expected. The dspam client send the user in RCPT-TO while discussing to
the server.

The user that reported the problem proposed a patch to make dspam work as documented: use rcp-to if available, else use the user. I added the patch in attachment to this bug report.

[0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=730999