Sentio

Sentio is an open source email server and REST API that gives each AI agent its own real email address. It is built in Rust and runs on infrastructure the customer controls, replacing the usual chain of an IMAP poller, a parser and an SMTP relay with a single service. Inbound mail is checked for SPF, DKIM and DMARC, virus scanned and spam scored before the webhook fires, and those verdicts travel with the payload so an agent does not have to judge whether a sender was forged. Agents reply in thread over HTTP by passing back the original Message ID, and outbound mail is DKIM signed with the tenant's own key so it authenticates as the customer's domain. The server also handles MTA STS, DANE, three tiers of anti spam, and forwarding that survives DMARC. The design targets developers who need an agent to take part in email conversations, and platforms that serve many customers. Domains, mailboxes, API keys, rate limits, suppression lists and spam profiles all belong to a tenant, so one deployment can carry many customers without shared sending reputation. A mailbox is created with three API calls covering a domain, a mailbox and an inbound route to the application's webhook. Sentio comes from Truespar, the research arm of The Intelligence Company, and is released under MIT or Apache 2.0 at the user's option. There are no license fees. Commercial support, model bring up and performance work are offered as paid services by contacting the vendor, with no prices published.