When you are having login error and not able to access the email account, then you should opt for troubleshooting steps. These steps are described here which you follow to resolve login problem.
1. Read the login error message carefully, sometimes it shows “Wrong username or password.”
2. Re-enter the correct username & password of your email.
3. Delete the caches, cookies and browser history.
4. At the last, you can ring the Optimum Email Customer Care Number. Through this number, you can contact customer care and ask them for help.
5. Read More:- Optimum technical support phone number