What's the point of stopping an activity's campaign?

A campaign is a sending that you have done and that you want to stop to no longer give a recipient access to an attachment, for example, to be able to reply to you, to receive follow-up notifications for this sending, orto no longer follow the status...

In other words, to stop access to an attachment after sending an activity to a recipient, go to one of the activities, click on the "More" button and then on "Stop": (example with an electronic notification)

Then confirm the operation:

Once you click on "Yes" the campaign will be stopped.