One way to generate a test is from the Dashboard. You can email a PDF (or other format) report to yourself. If you need to setup a domain-level email service, vWLAN will prompt you and you can follow the link to complete that part (though it looks like you have that part setup).
Consider setting up a packet capture on the vWLAN interface (Administration > Traffic Capture). See vWLAN and BSAP Traffic Capture Guide for more info. After you test sending an email, stop the capture and download it. Use Wireshark to view the capture file. Enter a view filter for "smtp" to make it concise. This should reveal any issues with vWLAN's communication with the mail server.
Keep us posted on your progress!