How to send email with Postmark

Knock integrates with Postmark to send email notifications to your users.

In this guide you'll learn how to get started sending transactional email notifications with Postmark through Knock. We also cover provider configuration and additional data you can pass through to Postmark.


  • Attachments support
  • Delivery tracking
  • Link and open tracking
  • Per environment configuration
  • Sandbox mode

Getting started

You can create a new Postmark channel in the dashboard under the Integrations > Channels section. From there, you'll need to configure the channel for each environment you have.

Provider configuration

API keystring*The API key for your Postmark server
Open trackingbooleanShould the provider track opens on their service?
Link trackingbooleanShould the provider track link clicks on their service?
From email addressstring | liquid*The sender email address (can use Liquid tags)
From namestring | liquidThe sender name (can use Liquid tags)

Environment default settings

The following fields are optional and if set, will be applied to all email messages sent via this channel within the environment:

Reply-to addressstring | liquidThe reply-to email address (can use Liquid tags)
CC addressstring | liquidThe cc email address (can use Liquid tags)
BCC addressstring | liquidThe bcc email address (can use Liquid tags)
JSON overridesstring | liquidProvider API's paramater overrides

Additional data sent

Knock sends the following attributes along with your emails:

  • Meta.sender: always set to
  • Meta.knock_message_id: the message ID attached to this email
  • Tag: the key of the workflow this message was generated from

You can learn about the role of these Postmark attributes in the Postmark API documentation.

Recipient data requirements

In order to send an email notification you'll need a valid email property set on your recipient.