Easy to do just by resetting your hosting through cPanel. BEWARE though, a reset means wiping clean and a NEW start, so backup everything safely.
A reset will give you new servers (not 100% guarantee though, but high possibility) and a new IP (almost 100% guarantee).
Chat with support for any further instructions, tell them you wish to reset your hosting.........
But needless to say make sure that you are addressing the right problem before making work for yourself, I would first ask support to run a test email for you. Just to be certain it's not your mailer at fault.