This looks interesting! I have not played around with webmethods.io before, I’m gna have to check it out. Have you looked into the RDP (Rest Delivery Point) feature of the broker? It’s basically a way to integrate pub/sub with REST where you can configure the callback link to the email server in the broker directly without needing to use a webhook integration (like webmethods). That way you will have one less configuration to worry about, so basically it will be Publisher publishing events to the broker on a predefined topic and the broker will trigger the callback server url that is configured to send emails.
We have a codelab tutorial that talks about that you might be interested to check it out Event-Enable your REST Architecture with Solace PubSub+, Part 1