Most cold-email tools are a spreadsheet with a send button bolted on. NuMail is infrastructure: a real send pipeline, a unified AI inbox, a campaign engine and a shared warmup pool, built on your own mailboxes, exposed over a REST API and an MCP server.
Each piece is deep enough to be its own product. Together they run the whole outbound loop, from first send to booked reply.
A single per-lead queue that routes across Gmail API, Microsoft Graph and SMTP/IMAP with true per-mailbox throttling: 90s cadence, a 50→500/day ramp, local-midnight resets, bounce suppression and send-window controls. Your mailboxes, your reputation.
Learn more →A unified inbox across every connected mailbox with 2.4s median reply detection via Gmail Pub/Sub and Microsoft Graph. Claude classifies each reply and drafts an answer in your voice. Approve, edit or reject in one keystroke, or let the API do it.
Learn more →Build multi-step sequences with conditional delays, per-step A/B variants and automatic winner promotion at significance. Spintax and merge fields per mailbox, send windows per timezone, and a clean enroll → reply → booked funnel on every campaign.
Learn more →Every mailbox warms inside a shared, cross-customer pool with Gold / Silver / Bronze tiers based on real reputation. Human-shaped conversations, gradual ramp and spam-folder rescue keep deliverability high without you ever touching a warmup setting.
Learn more →Run outbound for clients like a SaaS. Stripe-Connect sub-billing, custom-domain white-label and per-client sub-workspaces, each with its own mailboxes, campaigns and analytics, billed on your own Stripe with your branding end to end.
Learn more →Every surface in the product is an API call. REST endpoints at www.numail.ai/api/v1 with idempotency, cursor pagination and HMAC-signed webhooks, plus an MCP server so Claude and other agents can run campaigns, triage the Unibox and send replies on your behalf.
A lead enters a campaign, the pipeline sends from a warmed mailbox, the Unibox catches the reply and Claude drafts an answer. The warmup pool feeds reputation back into the whole thing.
Leads enter a multi-step sequence with A/B variants and per-timezone send windows.
The queue picks a healthy mailbox and sends within rate limits across Gmail, Graph or SMTP.
Replies land in 2.4s, get classified, and Claude pre-writes a response in your voice.
Cross-customer warmup keeps every mailbox in the green so the next send lands in the inbox.
↻ continuous loopWhat the four pillars deliver once they're running together.
We replaced three tools (a sender, a warmup service and a unified inbox) with one. The Unibox alone gave us back two hours a day per SDR.
Send pipeline, AI Unibox, campaigns and warmup, on your own mailboxes, with an API for everything. Start free for 14 days.