Once you have installed the addin a background process starts analyzing your email conversations and identifying conversations that you actively participate in but whose recipients are not your Salesforce CRM contacts yet. In many cases you'll see that those are real opportunities that should be tracked in Salesforce.
The add-in will tag all such email threads in Gmail and Outlook for you so that you could easily find and examine them.
1. In Gmail examine the 'YoxelContact' label/folder.
2. In Outlook web client search for 'Category:YoxelContact'
3. In Outlook (desktop) apply the Category 'YoxelContact' filter