If I were to guess, it sounds like that email you got was vague on what they meant…I’m not saying you mis-read it, but rather, it should have clearly stated attachments to emails not a general reference to files ‘from’ emails… I’m not sure the author wasn’t aware of this either, which is regret-able. As to a third party integration, there isn’t an actual way to attach files to emails in IS and an integration would be limited to what IS is able to do. As I mentioned, the best that could be hoped for there is the filebox used with the link set in the email on the contact so that it would be easier to reference. Alternatively, a product like dropbox or onedrive or something similar, but they all would take some coding to make happen. At least, I’m not aware of anything that’s ready made to combine the action of uploading and linking a reference in the email when it’s recorded.