My mistake. but didn’t know i had to do it that way.
I changed the username and the password en the emailadres, and than i tested. But that wasn’t working. I eventualy tried to first save the settings, than open the email settings again and than test the settings and that did the trick.
Excuse me for the inconvenience and the misunderstanding.
The Guide, Email transactions and reports | Manager, on how to email explicitly warns you about this in a yellow caution note near the bottom. I guess the caution should be added to the guide about troubleshooting email, too.