The client is the commissioner of a newsletter or another mailing. In the easiest case, this client is the same one as the client in which your newsletter is sent. (You always see your delivery client on the top right side of your user interface.) But there can also be more complex connections. In this case, an additional client is needed.
Different clients come into play in these cases:
You send out several newsletters that you want to manage separately. Reasons for this may be:
In this case, you can set up different customers, different departments of your company, for example, as principals under Account > Client Management via the button Create new client.
You are an agency and send advertising emails for different customers that should be managed separately. Reasons could be
In this case, select your customer as the client in a campaign.