PDF attachments sent via email will not open

PDF attachments sent via email will not open

When my users attach a PDF template (an invoice, for example) to an email sent using Zoho CRM to a customer, the customers report not being able to open the attachment. This is happening at an alarmingly high rate. When we download the PDF from a template and then attach it using an email client, the user can read it fine. There is something wrong with the way Zoho is encoding the PDF or attachment when it is being sent via email. This is angering our customers, and I need a resolution!