In October, an official letter was issued that regulates this issue. It states that storing the image part of a hybrid invoice in its original form is mandatory if it contains relevant entries for tax purposes, such as booking notes.
An earlier version stated that providing an email address was sufficient to comply with the requirement to receive electronic invoices from 1 January 2025. It is now clarified that it is not necessary to have a separate email address to receive electronic invoices.
And as an example of other acceptable European invoice formats, the Peppol BIS electronic invoice format is mentioned in the letter, replacing the Italian FatturaPA format.