If you are receiving bounced emails containing spam that are sent to your email address, then your email address is probably being forged by a spammer. Email authentication can help stop this.
DomainKeys can be used if you send outgoing email through our servers. It also protects the email from being tampered with on the way by digitally sigining contents of the email. The signature is checked by the receiver using a public key published in the domain DNS records.
SPF (Sender Policy Framework) allows mail servers to detect and reject forged email addresses. SPF records help to detect spam emails that uses your forged email address. They are a special DNS TXT entry that gives details on which servers are allowed to send email from your domain. Using this information along with further information in email headers, forged email addresses can be detected.
To enable either or both of these, login to cPanel and click on the "Email Authentication" option. Enabling both is usually a good idea.