We have the experience with hotmail addresses, but also with other e-mail adresses, that notifications and login data may end up in the spam (junk) box. What you can do is to open the spam box and open the mail that comes from MijnPlanOnline. You can then indicate once that this is a safe sender. From then on, you will receive the messages in your inbox.
Wat could also happen is that login data has not been sent. If this occurs, please go to the account login on this website and click on ‘wachtwoord vergeten’. This way you will receive new data to log in.