[RHSeeger]

But that also bound you to your ISP in a way, because switching ISPs meant switching emails. It is better to have then separated.

[layer8]

ISPs could be required by law to allow the porting of email addresses, just like it happens with mobile phone numbers.

[RHSeeger]

How would that work? The email address generally has the ISP's domain name in it.

[layer8]

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.