Google and Yahoo ask people who send a lot of email to authenticate their domain, to let recipients unsubscribe with one click, and to keep spam complaints low. Their help pages give the current thresholds.
What HawkOpen does: every copy ends with a visible “Do not send me messages” link in one of seven languages, every campaign copy has a List-Unsubscribe header with one-click support that leads to the same choice, and addresses that unsubscribed or bounced hard are skipped later. What HawkOpen does not do: it does not set up or test SPF, DKIM or DMARC and does not measure spam complaints. If you use Gmail or Microsoft 365 with your own domain, your provider’s admin settings and your DNS host are where authentication is configured.