I have installed the component on a master and slave website but I don't arrive to reproduce the problem.
Personally, when I have created a contact on the slave site, I have been able to send email to the contact.
Perhaps you should have to check that the sender email adress is allowed by your hosting server.
A quick review of the code show me that it uses the From email address that is defined in the Joomla Configuration. Perhaps that you have provided a value in this configuration that make your provider reject to send the email.
You can go on
slave1.demo.jms2win.com and use the Q Contact menu entry.
This will send me an email