Since you already own a SmarterMail license and only want to add more mailboxes you can do this in the shopping cart or a price quote. To make the purchase through the shopping cart start here, https://www.smartertools.com/purchase/shopping-cart.aspx
, click on Upgrade or Renew License and login using the email address and password associated with your license key and SmarterTools account. Then select your SmarterMail key on the following page. Next you should see the options for upgrading your license, including upgrading the number of mailboxes.
Once you have completed the purchase you will need to login to SmarterMail as the system administrator and go to Settings > Activations > Licensing and click on Reactivate. You should then see your mailbox limit change to 500.
If you need any assistance with purchasing or reactivating give us a call at 877-357-6278, start a live chat, or send an email to email@example.com.
Customer Relations and Partner Specialist