Earlier quoted context omitted.
This is pretty much the worst response possible. Hard bounces mean that email delivery services are going to start automatically removing, or at least stopping delivery to, entire slews of email addresses. A lot of clean up is going to be needed as a result of this. To add some more details, when using a 3rd party email delivery service, those services will either black-list or just outright remove email addresses wh…
Yes. I email hundreds of thousands of Gmail users each week (yes, double opt in, they all want the mails!) and we immediately delete any user for whom any Gmail error comes up at all in order to keep a solid delivery record with them. Sounds like we might have deleted 80% of our list if we'd sent today..!
(And if no such thing is detected deleted quarantined mail addresses.)