Usually, you'll have a contract with your email provider or with a third-party which is your point of contact to the actual email provider. In the latter case, ask the third party who is the actual email provider.
Alternatively, you may check the Webmail URL which you are using to access your email account or the email account settings in your email client application / mobile phone. Both might give hints about the actual provider. Please get in touch with our support with that information if you still cannot figure out your provider.