Ruby client for MisarMail's transactional and marketing email API (misarmail.com): send mail, run campaigns and A/B tests, manage contacts, segments, templates and automations, verify domains and DMARC, validate addresses, track revenue and read analytics. 33 resource groups on one client, plus retries with backoff, typed plan-limit errors, SSE streaming, and constant-time webhook signature verification. No runtime dependencies beyond the stdlib.