Plain provides native workspace level auto-responses, however for more complex cases you may want to implement your own custom autoresponder. To achieve this you can set up endpoint(s) to be notified of one or more webhooks from Plain. We would typically recommend listening for the thread created webhook as this will allow you the option of responding to any Thread whether it was created via email, Slack or a contact form. If you want to only reply to emails, you can use the email received webhook. This will trigger for all emails, not just the first one in a thread, so you should check the isStartOfThread field provided in the webhook payload to ensure you only reply to the first message.
Note that if you subscribe to both thread.thread_created and thread.email_received you may receive two events for the same email, since we create a new thread for emails which don’t belong to an existing thread. In order to avoid replying to the same message twice please check the isStartOfThread field in the thread.email_received payload.
Once you have received an event and decided how to respond you can use the replyToThread mutation to send a reply back to the customer. See our API explorer or Typescript SDK for more details.