iCloud Logging session

You can get a copy of your iCloud data stored at Apple by following these steps:

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Sign in to your Apple Account on Apple's Data and Privacy page to access privacy management tools for your personal data.

This set of self-service tools is available to customers in over 240 countries and regions around the world and includes options to: 

• Get a copy of the data that you store with Apple that’s associated with your Apple Account. For users based in the European Union, United Kingdom, or Japan you can schedule a one-time or recurring request for certain data (including App Store information and app install and push notification activity), as well as view the status of a request for a copy of your data that you made through another service.
• Deactivate your Apple Account temporarily.
• Delete your Apple Account — and the data associated with it — permanently.
• Request a correction to your personal data.
• Transfer a copy of your data to another service (including your iCloud Photos collection and your Apple Music playlists) and view the status of a transfer that you requested through another service.
• Learn about the types of data that Apple collects.

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copied from: Understand and control the personal information that you store with Apple - Apple Support

But I don't think, that emails or login data are part of that information.

If you delete your emails from iCloud, they are deleted and can not be restored.

Delete and recover emails in Mail on iPhone - Apple Support