You can always see at a glance the list you are in, by looking at the drop-down menu far to the left of the screen, just below the MailUp logo:.
In case there is more than a list and the logged user has access, this is how the drop down menu will look like:
And the "add new list" link is also shown if the user is allowed to use it
In case there is only one list or the logged user has access to only one, the drop down menu will look like:
Among the settings you can modify here: