[thesuitonym]

You can already do this without changing anything. Just set your corporate mailserver to not accept mail from common community email providers. There's a reason nobody does this, and it's because it's a bad idea.

There is so much crossover between personal email and corporate email.

[dmurray]

My previous employer did this, and no one seemed to miss it. If you had a use case to add an exception (the most common was to send yourself a mail from your personal Gmail, to print something on the corporate printers) that was supported and straightforward too.