distinct_id parameter in the track event call) will be considered the recipient.

.recipient in the recipient field to send the notification to joe@example.com
- To enter an array of recipients, something like "recipients": \["recipient1","recipient2","recipient3"\], enter in the format.recipients\[\]. It would send the notification to all the recipients in the array.
- If the recipient is a nested event property key like shown below, enter it in the format .recipient.id.
- In the below array object example, if you want to send notifications to all the admins of an organization, enter the format .organization.admins\[\].user_id.