Congratulations. Your mail provider Spectrum expects you to connect to the internet and hence their mail servers using their internet service. the IP address in your posting is 192.241.134.11 this is registered to a virtual server company DigitalOcean. See https://myip.ms/view/ip_addresses/3237053952/192.241.134.0_192.241.134.255 or https://ipgeolocation.io/browse/ip/192.241.134.11 So I am guessing the IP is in a range bitdefender have contracted as drop off points for their VPN. Ones that are unacceptable to Cox. As the error message in the link you provided https://www.spectrum.net/support/internet/understanding-email-error-codes makes very clear. With the 1000 error translating on the page to this text. Your IP address has been blocked due to suspicious activity. If you’re a Spectrum customer using a Spectrum-issued IP, contact us. If you’re using an IP address other than one provided by Spectrum, blocks will remain in place until they expire. So really you have a simple choice. Get another mail provider or stop using a VPN. The whole point of a VPN is to obfuscate you geo-location by hiding your real IP address. Now lets consider some things. You mail provider want you to log in using their issued IP address to send mail. Facebook will probably bark about you moving and ask for validations as will ebay. Both use Geo-location to try and decide if you have been hacked. Any web site that personalizes stuff based on where you are, from google maps to Walmart offering the local specials catalog will all mess up. You will still be entering your real location into most web sites to get your local information displayed. So ask yourself exactly what this VPN is really going to do for you? It certainly will not anonymize you to many web sites (including this one) because you have an account and log into it and have already provided a load of personally identifying information.

Please tell us ... Have you sorted out your problem? And was it related to Bitdefender ??