Ok I found the culprit.
Strange one I have never come across before but somehow the remote server setting was "stuck". If you sent an email from any other account the email is delivered to the Gmail account, but, it seems when using the contact form the domain forwarding would not correctly check the MX records and basically gets held by the root user email account.
The "remote server" configuration, despite having the correct MX records for Google Gmail set and Auto detect server settings configured, was not checking the MX records and forwarding the form submissions.
Turning off the auto detect server settings and changing to "remote server" kicked in the correct configuration for the form send query and directed the email successfuly.
Testing using your own Gmail or using your own email would not correctly display or test the form submission as it was checking your recipient email server via the destination email, my clients server settings were failing because of the configuration outlined above.
Thanks for attempting to help, I had already run the tests to see if the form would send to another email address as outlined in my original post.
Anyway, problem solved.
