why am I getting the above message

That's because Joomla couldn't send the order creation notification email.

You should check that you can send emails with the mass mail function of joomla.
If no, the problem is that you didn't configure properly the mail options in the joomla configuration. Please ask your hosting company for more information on the correct settings.

If yes, the problem is that your email server is rejecting the emails because it doesn't like some of the settings in the Emails tab of the configuration of HikaShop.
It can come from the encoding, the add name option, the bounce back email option.
Again, you should ask your hosting company for more information on the correct settings.

Then, did you configure an email server on your computer ? Probably not, so that's normal that you have these errors.

Yes it's related t joomla setup.

If you want your website to be able to send emails, you have to configure the joomla configuration for that so that joomla can connect to an email server in order to send the emails.

Here is a page where you can see an example of configuration of Joomla in order to connect to your gmail account (if you have one) in order to send the emails (that's the acymailing email configuration but the joomla email configuration is the same. I'm talking about the right part of the screenshot):
www.acyba.com/en/support/documentation/5...ing-config.html#smtp