If you notice an increase in spam being sent to an email account for your site, utilize the tools available in cpanel.
1. Login to your cpanel http://SITENAME.COM/cpanel/ OR cpanel.SITENAME.COM
2. Go to 'Mail' and then 'Apache SpamAssassin' and enable it and then adjust the settings
3. Consider using 'Box Trapper' found under 'Mail' but please review the information first! (note for it to work you must enable it for the specific email address that's having spam issues (example@sitename.com), blacklists, whitelists etc. will have no impact if Boxtrapper is disabled for the actual email address)
Helpful Links:
cPanel User Documentation
https://documentation.cpanel.net/display/ALD/cPanel+User+Documentation
cPanel Tutorials
https://www.youtube.com/playlist?list=PLZk46idJS6s54hAX8K79_AY8brgBwPtHd
cPanel & WHM Documentation (Dedicated Server Clients & Resellers)
https://documentation.cpanel.net
WebHost Manager - WHM User Guide (Dedicated Server Clients & Resellers)
https://documentation.cpanel.net/pages/viewpage.action?pageId=1507786