Address book and auto-populating address when sending for signature

Hello,

I'm using Adobe Sign via Acrobat for my business.  There appears to be some kind of address book in the system, because when I type certain names in the "send to" box it will pop up with contacts, including contacts that I've never sent for signature before.  The problem is that I can't figure out where the address book is, or where it's pulling from.

Is it pulling from the cloud?  From Outlook?  From my local machine?  I'd appreciate any advice because there are people on there that I would never want to mistakenly send documents to.  This is kind of important.