This error happens when the SMTP authentication credentials are misconfigured/invalid.
To resolve this issue, follow these steps:
- Log in as a super user.
- Go to Administration – System – General Settings.
- Scroll down to the section ‘Email server settings’.
- Check the Email server settings and correct them as needed. If they are correct, try to use the same credentials in an email client to test if they work there too. If the issue persists after configuring the correct credentials, please contact us.