Hi, thank you for your test.
Have you reset the settings after your tests? I've found SMTP setting still there. Are you sure you posted your reply in the right thread?
I've tried setting PHP Mail in Joomla Configuration by myself but it doesn't work. Did I forget something?
Anyway, I'd prefer to use SMTP and I've already developed other sites that use SPPB's Contact Form with SMTP (same email provider and same configuration).
On these sites Submit button works properly and the "Submit Success Message" is correctly shown after the email has been sent.
So I guess there's something conflicting in this particular installation and my hope is that you, with your experience, can find what is interfering with the process.
Thank you very much
Kind regards