Update to 2.x?

CuteMailing Sysfolder now should be marked as module. In v1.x the Sysfolder had an special doktype. The "module" property is now used instead of the "doktype" property. Execute upgrade wizard to update old Sysfolders.

If you are using an old recipient list from v1 of CuteMailing, then you should install undkonsorten/typo3-cute-mailing-registeraddress or undkonsorten/typo3-cute-mailing-ttaddress (see here). Use the upgrade wizard to migrate the old recipient list types.