Check the SBCGlobal Email Server's Status
Verify that your email address and password are correct or not.
Check your internet connection speed is fast or not.
Optimize and Reset Your Internet Explorer
Password Recover or Reset.
Follow above given steps to Resolve SBCGlobal Email Login Page Not Loading Error
See Also this post:- https://www.bloglovin.com/@datarecovo/how-to-set-up-sbcglobal-mail-on-ms-outlook-8334137
https://datarecovo.mystrikingly.com/blog/how-to-configure-sbcglobal-email-account-on-iphone-ios