Why do I have to choose between two mailbox providers?

The public authorities has entered into an agreement with two suppliers of digital mailbox,  Digipost and e-Boks. The mailboxes are equal and both meet strict security requirements. You can choose which digital mailbox you want. You can have both e-Boks and Digipost, but you can only receive mail from the public to one of them. You can select this on your user profile on norge.no.