If you are viewing the Recipient Activity for an Email Campaign and see a larger-than-normal number of email "opens" and link clicks from one specific recipient, then it is most likely due to their email provider's firewall or security measures.

This can occur when a security filter "opens" the email to view its content and scan its links for suspicious activity and content. Some filters check the links and content once, while others may continually check and open the email over and over again, which accounts for those high click and open rates for individuals. In addition, when such systems check the campaign, it may "test" the links, which can lead to the email provider unintentionally "unsubscribing" the recipient from your emails.

This happens because the email server's firewall can see that your email has been sent from a bulk sender. Some email servers are wary of this because anyone can send from a bulk sender, including a spammer.

To help prevent emails from being opened or altered by firewalls, it is strongly recommend that you set your account up with Custom Email Address Domain Authentication. When your email address domain is authenticated, mail servers and firewall/security filters notice that your incoming newsletter's DKIM FROM address matches the DKIM record of our sending domain. Basically, it's a handshake between your domain name and our application, which tells your subscribers' mail servers that we're friends and we're safe to be sending your emails through our system. This greatly improves your emails' deliverability and helps prevent security filters from "testing" your links and marking your emails as spam.

To get started with the Domain Authentication process, you can refer to the steps in this guide.