Hello! You can quickly hop over to your Response page to see if the 'Pause' option is available when clicking the dropdown menu next to that mailing. If it isn't available, then I'm sorry to say that the mailing has already sent out too many to stop it. The way the mailing system works is that Emma creates the mailing and compiles the list of all recipients. Then the 'injectors' send those recipient email addresses over to a holding area. That holding area works super-fast, so it can send as fast as the injectors can work. That means that most smaller mailings can't be paused anymore; anything less than 5,000 recipients definitely can't be paused.
I quickly jumped behind the scenes when I saw your post and canceled the remaining mailings. Since so many had already gone out, though, there were only two email addresses that hadn’t yet received the mailing. I hope this helps, though!