MXToolbox

MXToolbox is best known for free DNS and blacklist checks, but the paid Delivery Center adds inbox placement analysis, complaint reporting, mailflow monitoring, configuration analysis, and domain impersonation protection. It is a practical utility layer for teams that want monitoring before a full DMARC suite.

An agent stack treats email as a two-way primitive. Inbound has to arrive as structured JSON a tool call can consume, sends have to be safe to retry when a model loop repeats itself, and every action needs an audit trail. A provider without inbound parsing only solves half the problem.

Against inbound parsing into tool calls and model-generated sends that must not duplicate, MXToolbox covers event stream, and does not cover inbound parsing, idempotency keys, webhook coverage, batch sending, SDK breadth, and multi-tenant support. Whether that gap matters depends on how central those are to the build.

• Inbound parsing: No
• Idempotency keys: No
• Webhooks: No
• Operating since: Not published
• Event stream: Yes
• Best published rate per 1,000: Tiers not published in comparable form
• Batch sending: No
• SDKs: None
• Multi-tenant: No

Not a sender. Useful for blacklist monitoring, configuration checks, inbox placement, complaint visibility, and sender reputation investigation.

Teams that want DNS, blacklist, mailflow, and delivery monitoring in one utility platform.

A small sender that only needs basic DMARC report parsing.