A microservice that implements a REST API for sending e-mail. Doesn't actually implement SMTP, it proxies to a real SMTP server.
Lightweight asynchronous task execution service. Tries to replace RabbitMQ and Celery for lightweight (Python specifically, for some reason). Randomizes when retriesare done. POST base64 encoded URL to an endpoint and when you want it to run, and it'll hit that URL at the right time.