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inboxbase.ai runs the messy half of cold-outbound email: domain provisioning, mailbox warmup, rotation across a pool, threading, deliverability monitoring. You send, reply, and read threads through one API. We run everything below the API line. If you’ve ever built outbound on top of raw Gmail or SES, you know the work that goes underneath: provisioning new domains every quarter, warming up mailboxes for weeks before they can carry real volume, rotating across a pool so no single mailbox burns its reputation, stitching replies back to the original thread when the next send comes from a different mailbox. 12m runs that as a service. You get a stable handle, an API, and a webhook that fires when someone replies.

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Three nouns

You’ll meet three things in the API. They’re enough to model anything we support.

Identity

Your unified send/receive identity. One handle, a pool of warmed mailboxes underneath that we rotate across.

Conversation

A thread between an identity and an external recipient. Replies stitch in by Message-ID; we track ownership across rotation.

Event

Something happened — sent, replied, no-reply timer fired. Pull or push, your choice. Same monotonic seq either way.

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Pick a starting point

Send your first email

Sign up, mint a key, send a message, watch the event land. About sixty seconds.

Build a sequencer

Multi-step cold outbound. We handle threading and the no-reply timer; your code owns the campaign state.

Live thread list

Combine the conversations endpoint with the events stream to render an inbox UI that updates in real time.

API reference

Endpoint specs, request and response shapes, error codes.

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What we don’t do

We don’t ship a campaign UI, a lead-list editor, or a built-in sequence builder. Those are the parts every team wants to brand and iterate on themselves; we ship the parts nobody wants to own. If you’re looking for “Mailchimp but with API access,” 12m isn’t that. If you’re building the sender for an AI agent, a CRM, a sequencer, or a transactional product where deliverability matters and you’d rather not babysit warmup schedules — keep reading.