This issue has been resolved. For future reference, please see below the fix.
OK, we finally isolated the issue. We have a Guenevere (discontinued) email scanning tool that all emails go through when leaving the company, it checks for certain file types in attachments that are disallowed, etc. The other thing it does is appends a disclaimer that “this communication is intended for the use of….yada, yada, yada” This disclaimer is what is being garbled.
The file that the disclaimer is saved as is a text file on the Guenevere server and the server adds the text to the end of all outgoing emails. We have a workaround that lets us NOT add the disclaimer to the end of specified emails, but I wanted to let you know that this is the issue, in case you either have someone with a similar issue in the future, or possibly have had an issue with Guenevere in the past.
Thank you for your time,