While sending a OneTouch email job you will have the option to remove duplicates as to help decrease your likelihood for unsubscribes and improve deliverability. 

Inside your OneTouch workflow you will see the option to 'View recipients' and then 'View Duplicates'

This option will provide you with a  view of any duplicate email addresses within your list of recipients.

The view will group them by email address, if the email address is showing, that indicates there is more than one recipient with that email address. Click the + icon to expand the email address to view the duplicate. 

You have a few options to help you make selections about your duplicate contacts. It is only optional that you resolve the duplicates, if you wish to send multiple emails to the same email address, often because the recipient may have multiple relationships with users in your account (example: Loan Officers and Realtors).