This extension provides a plugin that displays a double-opt-in form. Successful double-opt-ins are saved as TYPO3 objects in the database and can be exported using standard TYPO3 backend functionality. The extension is especially useful if you have to retroactively double-opt-in email addresses (because DSGVO coerces you to do this): Just implement the form and have your users/subscribers fill it out. You can also use this extension to force users to double-opt-in before downloading a file.
- german translation - some documentation