Email activation failed. This email does not exist in our records.

"Email activation failed. This email does not exist in our records."

I get the above error when I try to activate my email. I activated the server to server on my hosting service (Altervista.org).

To be specific in Altervista.org when I abilitate external connections I Read:

Server to Server connections:
"Allowed with no restriction"

"Every applications can use http connection through outside server using fsockopen() of the cURL libs.
Attention: for security reason in every connection is required a logging"

What I have to do?