Hi! My name is ***** ***** I will be assisting you. Let's get started!
The issue with email accounts are that they can be almost 100% anonymous if the account is created that way. There isn't a database that can be viewed to pull up an email address and determine anything about it that might help you.
Your own provider is the only one that can look up things such as when the forwarded was started and how long that has been going on. If they are unable to help you with that information then request a supervisor. If the supervisor is unable to help then the information is available on their servers but it could require a subpoena. If they can view the forwarded emails then they should be able to view the dates of those emails going back to give you an idea of the start date.
Cyber Crimes are handled seriously by the government so you can report it here: https://www.justice.gov/criminal-ccips/reporting-computer-internet-related-or-intellectual-property-crime
Reporting the issue won't help you with finding out account information but it can help with shutting down a rogue account if it has happened to other people.
To sum everything up, there isn't a way for myself or anyone other than Suddenlink to view any information about the issue. I know that you have started with that method but I would suggest going back to them and pressing harder. The good news is that your account is now back in your control and I would recommend a password ***** to be performed as well.
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