Hello @bibeldans ,
We appreciate your consideration of using the weMail. We are sorry for the experience that you are having, but till now we haven’t received or faced such an Error. That’s why it may hard to provide the solution with a single word.
After receiving your concern we have analyzed your Error and it seems like maybe there is a problem with your SMTP credentials. Or it’s not the exact SMTP credentials. Is it possible to make sure again that you have gathered SMTP credentials correctly and you have confirmed on weMail in the right way?
And if possible please share a screenshot of your SMTP credentials and your weMail fields credentials. You can share screenshots by making sensitive information blur. If you can do that it will help us to dialysis the scenario more investigative way.