Most internet services are very low cost to offer for any company that has some infrastructure setup already. So for instance 'back in the day', before Google hoovered up everybody's email, what would typically happen is you would get an email address with your ISP.
> So for instance 'back in the day', before Google hoovered up everybody's email, what would typically happen is you would get an email address with your ISP.
Well, no, not even close. You'd get an email address from your ISP. You still do; nothing about that has changed.
Among the things that haven't changed is that you were more likely to use a free online email service, most notably Hotmail or Yahoo.
Similar as it happens for phone numbers, where there is internal routing of phone calls between providers. A customer can be at a different provider with their phone number than the provider who “owns” the containing block of numbers.
