If your web host company offers you a cpanel access, you will find there access to a tool called SpamAssassin.
There, you've two main options: the Spam filter and a White list.
Using the first one, you can define email patterns like
*@hair.com which mean: immediately kill those emails on the server. The second one is just the opposite f.i.
*@my-own-company.com saying that you trust that domain.
If you're hosted by PlanetHoster on the N0C infrastructure, please read Exterminate them all, fight spam directly at PlanetHoster - N0C instead.