You can use the permitted mailing list plugin for this.Mail addresses that are allowed can be allowed with this plugin.Another add-on that is slightly different is that you can set the not allowed mailing list.2. With the add-on, you can list the service names of such fraudulent users.But this is a situation that wants an alternative solution, there are many fake members who come using Gmail.As a solution to this in my own site, I want trust verification from Google, Yandex, you can add this to DMC rules. So, for example, when the recipient of the sent mail becomes a member within 24 hours, you can get a reject mail response. This is not a solution. Some real members can log in with a new post.But the second most effective method is SMS verification and 2 factor verification method.Another method is crediting, although it is not very valid for you dating system owners.You can control an incoming member with the credit earning plugin. Thus, when the member wants to access the xxx feature by logging in, it will be blocked.Finally, you can use IP Block Patri's extension, and it can provide good methods. Of course, you can try the ArtMedia plugin.