Custom fields are used in the recipient database records that store information about your recipients. You can add as many custom fields as you need. The added fields will extend the amount of information you can store with every recipient in your database. These fields can also be used in message templates in form of macros for the purpose of message personalization. The macros referencing to the custom fields will be replaced with the actual information taken from the recipient database when the final message is sent to the destination.