Plugin is failing with rspamd integration

[simonszu]

I am using your plugin, merely the @guoyiang s fork (because of #5) and i have noticed that it doesn't play very well with haraka-plugin-rspamd. When i enable both plugins, rspamd fails. Since rspamd doesn't fail, when i enable alias-forward, i think it could have something to do with this plugin as well.

Please notice haraka/haraka-plugin-rspamd#5

@guoyiang if you will receive this, it would be great if you could open up the issues section on your fork, since it is a bit different of @chadsmith s implementation.