If your IP is warm enough for 300M emails, you wont have a problem.
However if you normally send ie 10k emails a day, its likely that 90% of this 300M messages will be blocked by ISP's or redirected to spam and your send IP is rekt + sender domain score in the gutter.
It will take months to recover.
It doesnt matter to where your redirect from your CTA's, this can be Google or your own website. It matters from which domain Email is sent from, and obviously if you have configured it properly on auth side - DKIM, SPF, MX records etc.
If your IP is warm enough for 300M emails, you wont have a problem.
However if you normally send ie 10k emails a day, its likely that 90% of this 300M messages will be blocked by ISP's or redirected to spam and your send IP is rekt + sender domain score in the gutter.
It will take months to recover.
It doesnt matter to where your redirect from your CTA's, this can be Google or your own website. It matters from which domain Email is sent from, and obviously if you have configured it properly on auth side - DKIM, SPF, MX records etc.