If you have CPanel installed on your hosting account, which is pretty standard, you will have access to several good spam tools. Here is how to set them up.

First and easiest are the email filters. Go to email and click on User Level Filtering:

In the next screen you will see a list of all the email accounts you have set up. Next to each one you will see the link Manage Filters. Click it next to the email address you want the filter for. On the next screen click Create New Filter.

Now you can make a custom filter to automatically throw out any email with certain subjects or from certain domains, per your preferences:

For instance, you could add something like: Subject, Contains, penis enlargement, and send all such messages to the trash.

You'll have to be careful with these kinds of filters, as they can inadvertently catch legitimate email.

Another spam countermeasure in CPanel is Spam Assassin. All this requires of you is to turn it on. It's under Mail and then Spam Assassin. Enable it by clicking the button at the top, and then enable Spam Box as well:

Spam Assassin is automatic, but the settings can be configured if you are an advanced user. However, we don't recommend messing with the settings unless you know what you are doing. It works well by just turning it on.

Next, go to Box Trapper on the Mail screen. Again, all you have to do is switch it on for each email address. Setting can be configured but it's fine right out of the box: