Email not being received

Do you want to send me a screenshot of your Mail Settings?

Since the form is sending one of the two emails, the rest has to do with server configurations, rather than with Rapid Contact Ex or even Joomla itself.

Please switch SMTP Authentication to Yes and fill in your email and password.
The SMTP host may not be the localhost. It may be something like mail.mavrosxristoforos.com.
You can find this information in your host control panel, like cPanel or Plesk. You can also ask your host for information on setting up an email client.

Thanks again!