The issue has been resolved. If you have any questions do not hesitate to contact support.
Posted 19 days ago. Mar 06, 2019 - 22:31 CET
We're experiencing issues with our SMTP API. This results in some e-mails being rejected with different error messages. Your system can try resending the e-mails and our SMTP API should accept it without issues.
The issue is only affecting clients who use the SMTP API to send transactional e-mails.
We're investigating the issue and will update this ticket when we have more information.