Some messages bring replies that are of interest to many subscribers.
For example, a number of people might want to learn whether students at your school receive credit for work on a publication or what you consider the best way to handle a certain staffing problem. Other replies are intended only for one person and do not concern other subscribers. I hope to see you at the convention next week. If you use the reply function of your e-mail software, the reply will go to everyone who subscribes to the list.