Changelog

Groups & domains in the REST API, full SDK coverage

• Groups — full CRUD over /v1/groups: list, create (from contact ids and/or emails), retrieve with members, rename / replace members, and delete. POST /v1/groups/{id}/contacts adds members incrementally without duplicating existing ones. See the groups reference.
• Domains (read-only) — view a project's sending domains and their verification status via GET /v1/projects/{id}/domains and /v1/projects/{id}/domains/{domain}. Domains are still added and managed from the dashboard. See the domains reference.
• SDK parity — the mailer123 Node SDK now wraps the whole API: contacts, groups, campaigns, templates, projects, and projects.domains, plus a projectId option for multi-project keys.
• MCP — added read-only list_domains and get_domain tools.

AI access & docs search

The platform now speaks the Model Context Protocol (MCP), so AI assistants can run your workspace in natural language.

• MCP server — connect Claude, ChatGPT, Cursor, or any MCP client to a single hosted endpoint and have it send mail, manage contacts and groups, build templates, launch campaigns, and read analytics. It authenticates with your existing m123_ API key and runs the same guards as the dashboard. See the MCP guide.
• Docs search — press ⌘K anywhere in the docs to fuzzy-search every page by title, topic, and keyword.

Attachments, an SDK & a docs site

• Attachments — POST /v1/emails now accepts file attachments (inline base64 or a URL we fetch), and templates can carry reusable attachments that copy onto a campaign when applied.
• Node.js SDK — a typed mailer123 package wraps the REST API for server-side integrations.
• Docs & API reference — a full documentation site with server-side syntax highlighting and copy-paste code groups, plus a top-level API section in the dashboard.
• Pooled billing — plan limits and usage are now pooled across all projects an owner controls.

Public API launch

The v1 REST API is now available.

• Emails — POST /v1/emails sends a single transactional email synchronously and returns the message id, with html + optional text, reply_to, and unsubscribe-footer templates.
• Contacts — full CRUD over /v1/contacts, including custom fields.
• Campaigns — GET /v1/campaigns and POST /v1/campaigns/{id}/send to start a draft or scheduled campaign.
• Templates — GET /v1/templates and GET /v1/templates/{id}.
• API keys — create per-workspace keys (prefix m123_) from Settings → API, with full or sending scopes. Keys are shown once and stored hashed.
• Rate limiting & errors — 10 requests/second per key with a Retry-After header on 429, and a consistent { "error": { "message", "code" } } envelope across every endpoint.

Teams, deliverability & sending at scale

• Projects & teams — workspaces with invites, project settings, and a verify-email banner; every record is scoped to its project.
• Domains & reputation — verify sending domains, view per-domain reputation, and mirror bounces/complaints to your suppression list automatically via SES webhooks.
• Campaign wizard — a step-by-step compose flow with audience validation, personalization, and a live preview.
• Templates — reusable name + body templates with draft / published status.
• Contacts — file import, groups, and custom-field merge variables.
• Sending pipeline — campaigns send through an SQS-backed pipeline with dispatch reconciliation, built for scale.
• Domain warmup — a gradual-send engine that ramps volume on a new domain.

Validation, unsubscribe & reputation guard

• Address validation — an import pipeline that runs SES email-address insights and flags low-confidence, disposable, or undeliverable addresses before they cost you a bounce.
• Unsubscribe pages — customizable, branded unsubscribe pages and footer designs.
• Reputation guard — per-workspace bounce/complaint monitoring that auto-pauses sending to protect deliverability, with plan-based billing.
• Custom contact fields — per-workspace fields that become {{token}} merge variables.
• Activity timeline — a unified per-contact history of lifecycle and engagement events.

Foundations

• Analytics — per-domain metrics, a searchable mail log, domain detail pages, and contact-growth charts.
• Suppressions — team suppression management and an end-to-end unsubscribe flow.
• Content checks — a spam-check panel for templates and campaigns, plus email-syntax and disposable-domain validation.
• Sending — the first SQS-backed send pipeline with a Lambda worker.
• Dark mode — theme support across the app.