I'm sorry, but the provided knowledge sources do not specify the version in which the

transient_payload

was introduced in Ory. You may find this information in the Ory's version release notes or changelog.

The placeholders you're trying to use (

${SMTP_USER}

,

${SMTP_PASSWORD}

, and

${SMTP_HOST}

) are environment variables. These variables should be defined in your environment before they can be used in your Kratos configuration. If you're having trouble using these placeholders, it could be due to a few reasons: 1. The environment variables are not set: Make sure you have set these environment variables in the environment where your Kratos instance is running. 2. Incorrect syntax: Ensure that the syntax you're using to reference these environment variables is correct. The correct syntax for referencing environment variables depends on the context in which they're used. In a shell script, you would typically use

$VARIABLE_NAME

or

${VARIABLE_NAME}

. 3. Environment variables are not being read: If you're using Docker, for example, you need to ensure that your environment variables are being correctly passed to the Docker container. If you're still having trouble, could you provide more details about your setup and the exact error message you're seeing? This would help in diagnosing the issue. Please note that the provided knowledge sources do not contain specific information about using SMTP placeholders in the Kratos configuration. For more detailed information, you may want to refer to the [Ory Kratos documentation](https://www.ory.sh/kratos/docs/).