Licensing Plan Synology MailPlus comes with 5 free email accounts and allows you to add more accounts with additional purchased licenses. We provide two kinds of license packs to suit your needs: 5 or 20 units of email accounts1, both with perpetual validity2. The included licenses can only be applied to one Synology NAS, and cannot be migrated3 to another Synology NAS once activated. In addition, email aliases are not considered as email accounts and therefore do not require any license for use. To know the recommended number of active email accounts for each MailPlus supported model, please visit the product overview page, and go to the model's Specifications page for information. Notes: _____ 1.Once the purchased license key is applied, all its included licenses will be activated at the same time. 2.The activated licenses remain permanently valid unless the registered Synology NAS is down. 3.For any special need for license migration (e.g. RMA products), please contact Synology Support team for further assistance. High-availability Architecture No additional fee will be charged for the high-availability support in MailPlus, and one cluster includes 10 free mail accounts by default. To have more licensed email accounts for use, you need to apply purchased license keys from Synology. For example, if you want to enable 25 email accounts in the high-availability cluster, then 15 additional licenses are needed. MailPlus Web Client and Mobile App MailPlus web client and its mobile app (available for Android™ and iOS) do not charge fees for use, and they will be updated regularly for free with MailPlus Server. License Activation and Account Management To apply purchased license keys, you will have to log in to the Synology NAS as the administrator. Then, open MailPlus Server and go to License to apply the keys (Internet connection required). One license key can only be applied to one MailPlus supported Synology NAS. To activate or deactivate email accounts, go to Account for management. To check all your activated licenses, please log in to your Synology Account