/ Choose Logto: The better auth and identity infrastructure if
Its stated focus matches what you need: Logto is an open-source Auth0, Cognito and Firebase auth alternative for modern apps and SaaS products, supporting OIDC, OAuth 2.0 and SAML open standards for authentication and authorization.
/ Choose Plunk | The Open-Source Email Platform if
Its stated focus is closer to your workflow: Plunk is the open-source, affordable email platform that brings together marketing, transactional and broadcast emails into one single, complete solution