Explanation
The Sender Profile is the setting that allows you to configure the From Name, From Email, and Reply Email for a send. This can help identify the line of business sending the message. The Sender Authentication Package is a feature that enables you to use your own domain in your email links, images, and reply addresses. The Brand Builder is a tool that helps you create a consistent look and feel for your emails, landing pages, and microsites. You can learn more about these settings in the Email Creation and Sending module on Trailhead.

Explanation
If you want to ensure the exclusion is updated before the audience query runs, you should place the audience SQL Query Activity in a step after the exclusion SQL Query Activity. This way, the exclusion query will run first and update the data extension with the subscribers who should be excluded from the send. Then, the audience query will run and pull the subscribers who meet the criteria for the send, excluding those who were filtered out by the previous query. Placing a wait step between them or placing them in the same step will not guarantee that they will run in the correct order. You can learn more about this in the [Automation Studio Basics] module on Trailhead.

Explanation
Configuring the Journey Entry Event to 'allow no re-entry' will ensure that subscribers who have made recent purchases will only receive a thank you email the first time they show up in the file drop. This will prevent them from receiving duplicate emails if they make multiple purchases. [Source: Trailhead]

Explanation
The List Unsubscribe header is a feature that allows subscribers to unsubscribe from an email by clicking a link in their email client. This feature does not require RMM to be enabled in the account, and it can generate unsubscribe reasons related to RMM

Explanation
The auto-suppression list is a list of subscribers who should not receive any commercial messages from your account. You can add subscribers to this list manually or automatically based on certain criteria, such as spam complaints. This will prevent the subscriber from receiving further commercial messages from your account.