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 when they get a hard bounce "email address no longer exists" message back.
Some providers make re-adding an address after a hard bounce a non-trivial task, since after all, the authority on that email address just said it doesn't exist.
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 when they get a hard bounce "email address no longer exists" message back.
Some providers make re-adding an address after a hard bounce a non-trivial task, since after all, the authority on that email address just said it doesn't exist.
This is going to be really ugly.