Packages: each release publishes .deb and .rpm packages for x86_64 and arm64, which install the binary, the systemd unit and the engine's system user; nitromta-bin on the AUR; and macOS binaries for Apple silicon and Intel, for capture mode.
Homebrew:brew install nitrosend/tap/nitromta, on macOS and Linux.
Benchmarks: NitroMTA, KumoMTA and Postfix measured by the harness on an AWS c7gd.metal server, each committing every message to disk before accepting it: 3,313, 1,048 and 806 messages a second (benchmarks).
The benchmark harness:cargo harness builds NitroMTA, KumoMTA, and Postfix with OpenDKIM from source and measures each on the same machine under the same rules. Its profiles cover throttled and distant receivers, the backlog, the SES API, and crash recovery, including killing the process under load.
The SDK matrix:cargo xtask sdk runs the official SES v2 SDKs against the engine, each pinned by its lockfile: @aws-sdk/client-sesv2 and Nodemailer's SES transport in JavaScript, boto3 and django-ses in Python, and aws-sdk-sesv2 in Ruby.
Migrating from SES: a guide to moving an application, its domains, events, suppression list and templates from Amazon SES.
The SES v2 API:SendEmail and SendBulkEmail, by simple, raw or template content; email templates, kept and sent by name; identities with Bring Your Own DKIM, verified by their DNS records; configuration sets and their event destinations; tenants and their associations; reputation entities; the account; the suppression list; and dedicated IPs and pools. Signed with Signature Version 4 by access keys scoped to identities and tenants.
Events: SES-shaped Send, Delivery, DeliveryDelay, Bounce and Complaint events published through an SNS subset to HTTPS subscribers, and native subscriptions posting signed batches, retried, parked and replayed.
SMTP submission with STARTTLS and AUTH PLAIN, honouring SES's X-SES-CONFIGURATION-SET, X-SES-TENANT and X-SES-MESSAGE-TAGS.
Delivery: DKIM signing, STARTTLS, MTA-STS and DANE, an egress per sending IP with its own HELO name, per-receiver connection limits and throttle cooldowns from a bundle of receiver rules, retries on a jittered schedule, and expiry.
IP warmup: daily caps at each receiver for each egress, judged daily from what receivers said, with mail a cap has no room for put off in the store.
Feedback: delivery status notifications and complaint reports matched to their mail by its return path, suppressing their recipients, with reporters authenticated by DKIM when the operator asks.
Capture mode, which runs the whole engine on one machine and shows each message in a browser instead of sending it.
The CLI:setup, doctor, explain, queue, list, pause, resume, drain, parked, replay, backup, restore with its fence, migrate, check, and key rotation; health and Prometheus metrics.
Durability: every acceptance committed with a synced write before it is answered, tested by failing the power at every I/O operation and by moving a store to a new host.
Encryption at rest of personal data, off by default for a store on an encrypted disk: under the installation's key, or each tenant's mail under a key of its own, so removing the tenant erases it ([store] encryption).
Hooks compiled into a build of one's own, for admission and dispatch.
Hardening: the engine refuses to run as root, seals the secrets it stores under keys kept apart from its store, bounds every listener's connections and every request it has not yet verified, and runs under a hardened systemd unit.
