Salesforce Lightning
If you are using Salesforce Lightning, please follow the instructions in this article to learn how to create a Salesforce List View for any MassMailer related objects.
https://trailhead.salesforce.com/en/content/learn/modules/lex_customization/lex_customization_list
Salesforce Classic
If you are using Salesforce Classic, please follow the instructions in this article to learn how to create a Salesforce List View for any MassMailer related objects.
https://help.salesforce.com/articleView?id=customviews.htm&type=5