Call Axene from any n8n workflow with the built-in HTTP Request node.
Set the method to POST and the URL to https://mail.axene.io/v1/emails/.
Add an Authorization: Bearer axm_k_live_... header and a JSON body with from, to, subject and html.
Feed fields from earlier nodes into the body expression and run the workflow.
A dedicated Axene n8n node so you skip the raw HTTP setup is on the roadmap.