site xyz.net.au is not on any blocklist, has good reputation in senderbase.org. It can send emails to any gmail/ google hosted mail server, BUT the email is stripped of any attachment. The attachment is always a .pdf, not .pdf.exe. I need a contact number/ email for 'outside' admins to interact with google, or failing that, a solution that doesn't involve changing the IP address.
Have you sent one to an account you can access via the web to eliminate server or Outlook issues?