Internet Service Provider (ISP) is the generic term for providers of all sorts of Internet services: connectivity, bandwidth, mail, DNS, web hosting, etc. Network Service Providers (NSP) and Email Service Providers (ESP) are specific kinds of ISPs. Your ISP is the company you contract with for your Internet services. You should contact them regarding any service problems, including SBL listing!
Want to have a trail run for your campaign? Do you want to test the quality of the service we offer? One of our customer advisers will call you to discuss about your requirement and set up a free trail account for you.