Sending email when developer signed up using REST API

When developer registers in the customized developer portal, I create a developer account using the below REST API.

When a developer is created, I would like to send welcome email to the developer. I configured “email_backend” in tyk_analytics.conf but the email is not sent. I think that it doesn’t work with creating developer with REST API. Can I make it work with this REST API?

I’m testing this with Tyk onPrem.