When the Email this address after an automatic IP ban setting in the Configure WAF page is non-empty you will see a red (error / attention) message at the top of every backend page reminding you that receiving an email for each and every blocked request is only meant to be used as a temporary troubleshooting measure, not a permanent option. The reason is that during a sustained attack the number of emails your site will try to send you will slow your site down to a crawl and overrun your mailbox.
You have the option to disable sending emails on blocked requests, or dismiss this warning forever. This is a manual action you will need to take when you visit your site's backend after installing version 7.7.0 if the Email this address on blocked request feature contains one or more email addresses.