Standard-Delivery Validations and Checks for BP Data Model

Hello Experts,

I have an issue concerning  basic understanding of the inculded standard delivery field checks that come with SAP MDG-BP.

For example following E-Mail field-check which pops up after entering an invalid e-mail format:

Where can those rules be accessed and reviewed - I searched through the Badi implementations, but no luck

Thanks you for your help!