When does the validation of email address occur when using a data extension?

A file is received daily from a data provider to the account SFTP. This file needs to be imported into Marketing
Cloud as soon as it arrives. The arrival time of this file varies by several hours from day to day.
What tools should be used to accomplish this?

Northern Trail Outfitters is redesigning its brand guidelines and wants to ensure its emails are accessible.
Which best practice should the email designer follow to meet accessibility standards?

Northern Trail Outfitters (NTO) created several lists of subscribers, and would now like to send an email to all female subscribers.
Which feature allows NTO to easily target this segment?

Northern Trail Outfitters (NTO) is launching a post-purchase campaign that email customers to ask for feedback on their most recent shopping experience.
What should the NTO marketing team include in the email design to encourage a high response rate?