CompuServe was one of the earliest publicly-accessible online services, going back to the 1970s. Users dialed up with their 300, 1200, or 2400 baud modems and paid sizable hourly fees (even higher in the daytime when CompuServe's network was being used by business customers) in order to access various features including e-mail, chatting (called the "CB Simulator" after Citizen's Band radio), and an early version of e-commerce (various aspects of which have actually been cited more recently in efforts to invalidate various patents created by people claiming to have invented ways to buy and sell things online through the Web which were actually done much earlier on CompuServe).
Eventually CompuServe was acquired by AOL (something much disliked by CompuServe's members who typically regarded themselves as superior to the clueless newbies who used that other service) and it eventually migrated to the Web, where a remnant survives mostly as a news portal.
Users on the classic CompuServe were identified by numeric user-IDs consisting of two strings of digits separated by a comma, like
72057,3267. This was used as the user's CompuServe e-mail address. Later, when CompuServe was connected to the Internet, the comma was converted to a dot to put to the left of the @ sign, followed by compuserve.com (
email@example.com), to make an Internet-style address. Right-wing talk radio host Rush Limbaugh, who used CompuServe at the time and often announced his address there on the air, famously claimed to ignore all Internet messages he received there, because Internet users were worthless hippies who didn't pay for their own connections as did CompuServe users. (At the time, the Internet was still primarily an academic network.)