I found the “issue”.
I had another mailing provider (Postmark) installed as a plugin, which I brought in my local site by mistake. That prevailed over any other mailing configuration.
I deactivated the plugin and now my hook works fine.
I found the “issue”.
I had another mailing provider (Postmark) installed as a plugin, which I brought in my local site by mistake. That prevailed over any other mailing configuration.
I deactivated the plugin and now my hook works fine.