Sandbox servers are servers that will never send messages to a recipient. Instead, the messages are delivered to a black hole. That means your test messages are visible and will appear as Delivered in Postmark’s UI, webhooks, API endpoints, etc., but won’t actually reach a real inbox. This lets you use the Postmark API or SMTP sending, without fear of accidentally sending messages to real addresses.
❗️ Good to know: Even though test messages aren’t delivered to real inboxes, we still process them through Postmark’s infrastructure and our API remains accessible for these messages. That’s why emails sent through Sandbox Servers do count towards your monthly sending volume.
When creating a Server, you’re given a choice to set up a Live Server—that’s a Server that will deliver email to recipients—or a Sandbox Server for testing. To create a Sandbox Server, choose Sandbox.
Once a Server is created with a specific type (Live or Sandbox), it’s not possible to change the Server type.
When using the Servers API to create a Server, it’s possible to set DeliveryType to Sandbox. This value defaults to Live if no parameter is passed.
Once a Server is created with a specific type (Live or Sandbox), it’s not possible to change the Server type.
