When logged into the Match My Email cloud, you can view emails that have been imported into the cloud, whether they are matched or not. If an email is a No Match status, it often indicates that individual is not yet in Salesforce as a Lead or Contact. In some cases they may be using more than one email address for communication and only one email address is in Salesforce.
If seeing only No Match status messages would be more efficient, you can filter the cloud for only No Match per steps in this wiki post.
B-1. Create a new Lead