Check mxtoolbox.com or https://www.abuseat.org/. CBL will give you more details on what website in the IP address range is causing the problem. Try a plug-in to check your site for any spam or malware (e.g. Wordfence on Wordpress). GoDaddy may try to help, but we have not had much success. They did not detect the problem with the GoDaddy website causing the problem and it has taken three calls and a set of emails just to get GoDaddy to change our IP address. After two weeks, they have not successfully changed it. Nice techs, but not competent.
The IP addresses change every so often so you may have to wait a month or so for the address to cycle to a new one. Sorry, but good luck.