To have the save action for your form actually send email, you will need to change one of the settings, otherwise you will receive this error whenever submitting the form:
We experience a technical difficulty while processing your request. Your data may not have been correctly saved.
Also in your log (/data/logs/newest log file) you will see this error after the form has been submitted:
Message: The remote name could not be resolved: 'example.host'
at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6, Int32 timeout)
at System.Net.PooledStream.Activate(Object owningObject, Boolean async, Int32 timeout, GeneralAsyncDelegate asyncCallback)
at System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback)
at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout)
at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)
at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
WARN Web Forms for Marketers: an unhandled exception: Failure sending mail. has occured while trying to execute an action.
In your content tree, browse down to: /sitecore/system/Modules/Web Forms for Marketers/Settings/Actions/Save Actions/Send Mail
Under that item there will be a submit section with parameters:
Just replace example.host with your SMTP host information for the server, and firstname.lastname@example.org with the address you want to send mail from – save, and republish!
That should correct the error above and, barring any other issues, hopefully the form will be working as intended!