Postmark Server defaults to Transactional Stream

Your software
My Mautic version is: v3.1.2
My PHP version is: 7.1.33

Your problem
My problem is:
Postmark offers two streams

Transactional -
Marketing - Broadcasts
The default server when selecting postmark in the config is

Steps I have tried to fix the problem:
I tried changing it in app/bundles/EmailBundle/Swiftmailer/Transport/PostmarkTransport.php

But it still defaults to transactional stream

I also tried editing local.php ‘mailer_host’ => ‘’,