Receiving message – Cannot load checkemail.

So I am having an issue with my email on my WP site and one of the suggestions was to use this plug in Check Email… but even with this I am getting an error…

Cannot load checkemail.

what the heck and I doing wrong? And how can I get my darn emails working on my WP site??

https://ww.wp.xz.cn/plugins/check-email/