When you send an e-mail with an attachment (via our plug-in) in Outlook, this will be automatically added to the 'sent items' within Outlook. You will see the attachments here, even though they have been sent securely.
From this place you can check which attachments are included and here you can open the files. The 'attachments.txt' is a text file that states which names of the attachments are included. This is always automatically added.