The contacts activity history is a log of all events sent to this contact.  It also shows you if someone has interacted with the emails and you are able to add notes to this contact record as well.  Click here to view the steps to access the activity history.

The Daily Marketing Preview tool shows you the e-mails from past, forward and current dates.  The daily marketing preview will show you when the email went out, who it was sent by, who it was sent to, which campaign they were on, and show you the exact piece of content with all the filled in merge codes.  You can use the search bar under the from, to, subject line and campaign name to filter the list of queued and sent emails.  To look for someone who should have gotten an email on a specific day you would want to filter the list from the 'To' column.  From the dates you originally sent, this will show you all the marketing that has gone out to that contact.