Spam is a serious problem, and fortunately, there’s an easy way to make sure that your domain doesn’t get caught up in the practice.
What you’ll want to do is set up an SPF record. To accomplish this, you can go to www.openspf.org.
This site will make the process very easy, and you will simply answer a few questions pertaining to how you want your mail to be handled. You will be asked if your mail server sends mail, in addition to accepting mail. In most cases, you will answer yes to this, as your mail server resides on your web server unless you have a dedicated server, and set things up otherwise.

You will then be asked if you want to approve any host that ends in your domain name. You will in almost all cases want to answer “no.” If you have additional MX servers (servers that send mail), you will need to enter them, so they can be authorized.
When you are all done, you will wind up with an SPF record that looks something like this:

“v=spf1 a mx ~all”

This would be entered into your DNS record under the TXT section.

The record shown above states that the mail servers openspf.org found do send mail (through SMTP), and that those servers are in fact the only servers that are authorized to send mail for that domain. You can discover more about the syntax on the site, and it can be customized to meet your specific needs.

After making your new SPF record, you will want to add it as a TXT record in your DNS zone files. Fortunately, this is quite easy to do with Cpanel.
Navigate to your Advanced DNS section under “Domains,” and then enter your domain name with a trailing period under “Name.” (example: ) Then, enter a value for TTL. You can simply enter a default 900 as the value. This sets how long it will take before the change goes live in your DNS. Next, you will want to click on the drop-down menu and select the “TXT” option.

Finally, enter the SPF record you created previously, complete with the quotes, confirming your changes.
Once this is completed, you will have an SPF record, which will prevent your domain from being misused by spammers or even your own users for the purposes of spam or other unsolicited mail activities. The most important thing is that it protects your domain from being “spoofed,” or making it seem as if mail is coming from your domain when in reality it isn’t.