Spam is an annoyance and there's a multitude of ways to counteract it. However spammers also get smarter and try to bypass filters and stuff. In addition, ICANN has lately approved a great mean gTLDs (generic Top Level Domains), like .biz, .info etc. Some of those gTLDs are, in my opinion, exclusive used by spammers. Lately, I have gotten a lot of spam from the .xyz gTLD. So the question was, how to block email coming from such domains using that gTLD.