The total mailbox size of your Sparklight (Cable One) email account is 20 GB. That's the cumulative size of all the subfolders, such as the inbox and sent. Internet and cable TV provider Sparklight will discontinue CableOne email service for its residential customers during the course of the. Cable One, Inc. (NYSE: CABO) is an American broadband communications provider. In summer 2019, Cable One, Inc re-branded themselves as Sparklight.