I know the answer to this question - The real reason I'm putting this on Adobe Acrobat Pro DC Forum is to raise the awareness of the severe limitations of the plug in for Outlook.
Sending a PDF as an attachment from Outlook (desktop) via Adobe Send & Track results in - every person will be "Anonymous". It doesn't matter who you "Send To", all are anonymonized. Adobe know this but it's not documented forthrightly; and that's my BIG beef. Below you will see the tracking results of my first and second send was to multiple people. I don't know who opened the PDF. That's pretty miserable tracking as far as I'm concerned.
However if you upload to cloud and send via Adobe's server, not from your local Outlook email account, I can only assume the recipients will be identified as individuals by their email address. Outlook Send history would be incomplete however. This plug in for Outlook is severely lacking.
My second issue is about tracking results in general. The results are so limited. As you can see the first doc shows my initial send as a test. The second is to intended recipients (7 email addresses in all between To, CC and BCC. We see the # of views but the date AND time are missing. For *od's sake, even if they have to resort to showing GMT at least I would get something other than a simple, single digit of "views".
Send & Track is still in it's infancy.