SPAM emails how can I make them STOP!?

Our website email has been getting spam messages from different people. How are they getting our email (it is not displayed or given out) and how can we go about blocking or stopping these messages? Examples of the spam:

Name: John Gillmire
Email: [email protected]
Message: I realized while I was on your website that you have a WordPress website. At first it seemed a bit sluggish and was a little slow to load. I also had this problem a while ago with one of my WordPress sites. Webhosts like Godaddy, Host Gator, Blue Host, etc often overcrowd their shared hosting plans which can be bad for your website, have you ever looked into this?

There’s a guide right on wordpress maintained by a member that shows you how to check for this in two easy steps. The guide is at:

[link moderated]
If you have a moment, it’s always a good idea to follow the two steps in that guide to test your current host. Your hosting is one of the most important factors for a WordPress based website. Good luck with your website!

Message: Hello,

Camealy Group has been PREAPPROVED and is eligible to receive business funding. We also have unique, discounted early-payoff options available. Please contact our PREAPPROVED department at (888) 610-3363 or https://www.prioritypaymentsystemsrsm.com/sign-up.html for personalized handling and Lee Casas will assist you to initiate funding.

Name: Lee Casas

Email: [email protected]

Message: Hello,

Private investor has $35,000 to invest in Camealy Group a local business, must be located in our around Hurlburt Field. No bank, no red tape, easy terms, fast approval. Larger amount is possible click here [link moderated] for approval.