Sometimes Hosting providers do not allow to send emails, to save server resources. For example free hosting providers, or depending on your subscription package with the hosting provider. Check their info or get in touch with them to see if this is not the case.
The other option is, you can use SMTP instead of the local mail. If you don't have one included with your hosting provider, you can try free SMTP servers. I heard Google has a free SMTP Server.
To edit your SMTP settings on Q2A, navigate to:
Admin > Emails > Send email via SMTP instead of local mail