Qmail, Qmail, Qmail, Why Are You So Complicated?

I found a new patch for my qmail server today. It's used to block clients from local area network to send email to blocked domains that are listed on qmail server. It's a pretty neat patch, I know, but sadly I still am struggling to apply the patch to my server. I just couldn't apply it recklessly, I need to test the patch on non-production machine first but, this is the problem, I don't have any extra server..... ;_;

Woe is me...