When you turn 15 years old, you are registered for Digital Post from the public sector. You must also have MitID, in order to access your mail. Some 15-year-olds already use MitID, for example to be able to access their bank account. If you don't have a MitID today, it's time to get one. Read here how to get started.
Get MitID with passport
Get the MitID app for your phone and follow the instructions.