To address the issue of Northern Trail Outfitters' employees not receiving emails due to spam filters, the Marketing Cloud admin should provide the IT team with a list of relevant IP addresses to whitelist in their spam filters. This action will help ensure that emails sent from Marketing Cloud do not get blocked by the company's email security systems, thereby improving deliverability and ensuring that internal communications reach their intended recipients.
Reference: Salesforce Help - IP Address Whitelisting

Explanation
To drive their mobile adoption strategy, NTO could use the following two report types from the Discover Reporting Tool:
* Email Performance by Device1. This report shows the number and percentage of email opens and clicks by device type, such as desktop, mobile, or tablet. This report can help NTO understand how their subscribers are engaging with their emails on different devices and optimize their email design and
* content accordingly.
* Time Between Send and Engagement2. This report shows the time elapsed between when an email was sent and when a subscriber opened or clicked it. This report can help NTO identify the best time to send emails to their subscribers based on their device preferences and behavior patterns.

To configure a journey using Path Optimizer with a holdback of 60% of the contacts until a winner has been selected, the Marketing Cloud admin needs to set:
* A. Data Extension entry source: Ensures the journey is pulling contacts from a specific data extension which can be effectively managed and monitored for the experiment.
* D. Winner evaluation: This setting allows the admin to specify how and when the winning path is determined, which is critical to managing the holdback and subsequent path optimization.