SPAM Email

If you use a Hosted Exchange or like service, they should filter for spam.
If you use your own Exchange that you manage, you could use something like the Barracuda spam filter. You did need something on top of Exchange.
If you are receiving email in a non-Exchange environment, you need a mail service that provides spam filtering like mail.com. I use mail.com

There are many, many ways to filter spam and no one solution fits all. The only thing I do not recommend is rolling your own because the problem has largely been solved commercially.