Open your contact form in edit mode through page "Contact > Contact forms". On edit screen select "Additional Settings" tab and make sure that in textbox above you don't have next text:

demo_mode: on

If so, just remove this line. Thus you disabled demo mode for your contact form. In this mode, the contact form will skip the process of sending mail and just display "completed successfully" as a response message.

Contact from edit screen

Is this Post useful? Useful Useless 1 of 2 people say this Post is useful.