We have a client who regularly forwards emails to one of our internal users that contains html attachments, which allows us to read and download secure messages. The internal main user who does this suddenly is receiving an email with an unnamed attachment, but if I save the attachment as an html file, I can open it, the web page redirects properly to the secure web page, and we can access the file securely. If this email is forwarded to another user, of even if the internal user who is having the problem forwards the email to another user, there is an html attachment. When the other user forwards the email back, the email then has an attachment with an html extension. I am unable to figure out why the emails are not showing up properly from the original source only, so any ideas would be appreciated.

This is for Outlook 2010, and I've tried to disable all plugins in Outlook, I've gone into Internet Options in the control panel and deleted browsing history, restored advanced settings, reset IE settings, and tried versions of IE9, 10, 11 on the system. Nothing helped. The system is protected with Vipre antivirus and Malwarebytes, and I've disabled/enabled these during troubleshooting.

Thank you.

• Edited by baskervi 16 hours 19 minutes ago