In the WHM console, click Backup Configuration, and scroll to the bottom looking for additional destinations. Since daDup.eu is Amazon S3 compatible, you may select Amazon S3 in the Destination Type and Create new destination.
While configuring it, give it a name and select the box that says transfer system backups to destination (traffic to daDup is encrypted so it is safe to select it).
Enter the name of the bucket you created earlier, access Key ID, and secret access key found in https://admin.tuxis.nl, followed by save and validate destination. Assuming you did everything correct, it should appear as an additional destination at the end of your backup configuration. Click Save Configuration and you’re done. Backups will automatically be transferred to daDup.eu as soon as they are done. You may run a test backup an check with Dragondisk if data is written on daDup.eu
One final choice is whether or not to leave the backups on the local drive for quick restores. Feel free to do that if you have the space. To do that, just click Retain backups in the default backup directory.