On the From tab, try leaving the form display name empty
If you click on the envelope icon, what are you using for an smtp server? You should contact your host to find the correct smtp server name to enter.
try checking the Include From Address as an additional option as well.
Have you set a redirect page for after the email is sent?
If it is still not working, please send a copy of you page and the webassist folder so I can look into the code.