Mass emailing and group emailing are two different methods of sending messages to multiple recipients. Mass emailing typically involves sending a single message to a large number of people, often with little personalization or segmentation. Group emailing, on the other hand, involves sending a message to a specific group of people who have something in common, such as being part of the same team or department. Group emailing allows for more targeted messaging and can be more effective in getting the right message to the right people.