When an application says “the email webhook never arrived,” split the path into two systems:
Mail path: application -> provider -> recipient system.
Event path: provider -> your HTTPS endpoint.
A delivered email with no webhook points toward the second path, not SMTP.
Check provider event logs, webhook subscription configuration, endpoint DNS/TLS, request authentication, HTTP response codes, timeouts and application logs.
Also check whether your endpoint accepted the event but failed later during asynchronous processing.