You should receive an initial email from Smartertools when you signed up that contains your specific License Key. If you did not receive your login information from SmarterTools, you can use the following URL to retrieve your password:
Disregard the instructions in the email regarding the download and installation of the program itself, for it is already installed on your server. Note the License Keys for each product.
Log in to SmarterMail as ‘Admin’
Click the Settings button at the top of the window.
Click the link for Activate Product in the menu on the left-hand side.
You should now see the Activation menu on the main page. Click the button which says Activate a License Key.
Enter your License Key as provided in the email. To avoid confusion, you can simply copy and paste the License Key directly into this field. Once entered, click Next.
Now, enter the email address registered with SmarterTools and the password associated with it, and click Activate Now.
You have now activated your License Key for SmarterMail, and will be able to add the amount of domains and users allowed with your particular key.