As an Admin, you have a special mailbox for messages related to the actions you take in the User Management tool. You will receive messages when usernames are bulk loaded into the system and when you move multiple usernames from one organization to another.
You will find the link to Messages in the left sidebar menu on any Admin Tools page.
When you click on this menu link, you will go to your Messages inbox. There, you can filter your messages to list all messages or only those you have not yet read. Just click on the subject of the message to read it. When you are ready to delete your message, you can either click on the checkbox next to the message in your message list, then click on the Delete tab, or open the message, then click on the Delete button.
If you need further assistance, please feel free to submit a Support Request.