We host a website for people to sign-up for events and athletic teams/sports. When people sign-up for said sport, an email is sent to that individual with a PDF attachment which is their receipt. If the person receives the email, the PDF opens just fine and all is right with the world. If the email is returned to us (invalid email, mailbox full, etc) the PDF is corrupt and we can't open it to print it to snail mail the receipt to the individual.
This occurs across multiple domains: Gmail, Yahoo, Hotmail, Comcast, AOL, Verizon, et al
Now, our website is setup to send email out directly through one of our Barracudas (Spam and Virus Firewall 300) and doesn't touch our Exchange (2007) setup at all. The email only touches Exchange should it be returned for whatever reason. Attachments can't be opened via OWA or Outlook (this was tried across multiple machines).
Opening a returned email brings up an error indicating a corrupt PDF file. I have tried running a PDF "Fixer" on some of these receipts to no avail - the PDF "Fixer" actually says there are no page numbers in the file. Also, one of our network guys noticed the files which leave are almost twice as large as the files which are attached if the email should get returned.
It's almost as if something is stripping code from the PDFs.
I'm at a loss.