If you're getting this error when sending out email, please double check your email settings are set as below.
For Microsoft Outlook:
1. Click Tools then E-mail Accounts.
2. Select "View or change existing e-mail accounts" and click Next.
3. Select the email account and click Change.
4. Click on "More settings".
5. Select "Outgoing Server" tab.
6. Tick "My outgoing server (SMTP) requires authentication".
7. Select "Use same settings as my incoming email server".
8. Click OK.
9. Press Next.
10. Lastly, press Finish.
Once these steps are done, try to send the email again. If it does not work, please contact us for assistance.