Bill.com invoice rejection...

I have a client sending invoices daily via Paperless Office.

One of their customers uses Bill.com to automatically receive invoices.

The Sage emails, when viewed in Outlook show one attachment which is the PDF file.  However, when the invoice is received into Bill.com, there are two attachments.  Also, the email subject line is adding a ".txt" at the end of the email when it is received into Bill.com.

Any thoughts on how to remove the ".txt" from the subject line?

Has anyone else seen this?