Does your host support sending emails using the PHP mail() function?
are you sure you are using the correct setting for the SMTP server address? perhaps try leaving the mail server blank.
Sometimes the email may be trapped by a spam filter, check your spam folders to see if it is being trapped as spam.
In Universal Email, have you entered a from Display name? Is so, try leaving that blank.
Make sure not to use the same address for the from and to settings. Some hosts will not relay emails if the from address and the to address are the same.
You may need to ask the host to look into the smtp server error logs to see why the email is not being sent.