High-Volume Sending

Send Millions.
Catch Every Reply.

The only cold email sequencer with full reply handling on high-volume sending infrastructure. Purpose-built for Mission Inbox OBM — one API key powers thousands of senders, and every prospect reply is caught, threaded, and managed in a unified inbox.

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Purpose-built for Mission Inbox OBM

One API Key

Thousands of Senders

Full Reply Handling

Automated DNS

AI Categorization

Rate Limiting

The High-Volume Sender’s Dilemma

If you’re sending 300k+ emails per month, every option on the market breaks in a different way.

Mailboxes Don't Scale

Buying 500 Google Workspace accounts to send 1M emails is expensive, takes months of warm-up, and Google actively fights this use case.

APIs Can't Handle Replies

Transactional senders like SendGrid and Mailgun can blast millions of emails, but they're one-way. When a prospect replies, there's no inbox to catch it.

Sequencers Assume Small Scale

Every outbound sequencer — Apollo, Instantly, Smartlead — is built around individual Google/Outlook accounts. They have no concept of a transactional API backend.

SuperSend + Mission Inbox solves all three. Volume of dedicated infrastructure. Experience of individual mailboxes. Every reply caught.

How It Works

From API key to unified inbox in four steps. No mailboxes to buy, no IMAP to configure.

Connect Your OBM API Key

Paste your Mission Inbox API key into SuperSend. One key gives you access to your entire dedicated sending infrastructure — all IPs, all domains, all capacity.

Create Sending Identities

Build hundreds or thousands of unique senders on top of a single API. Each gets its own email, display name, daily limits, and campaign assignments. Bulk import via CSV.

Emails Sent via Dedicated IPs

Campaign emails go out through Mission Inbox's dedicated IP infrastructure with automated warm-up. Threading headers are added for proper conversation continuity.

Every Reply Lands in Your Inbox

Replies route through SuperSend's mail server via MX records, match to the original outbound via threading headers, and appear in the unified inbox — fully threaded and AI-categorized.

Two Paths, One Inbox

Outbound emails go through Mission Inbox’s dedicated infrastructure. Replies route back through SuperSend’s mail server. Both meet in the unified inbox.

Outbound Path

Sending via Mission Inbox OBM

SuperSend CampaignQueues personalized emails

Mission Inbox OBM APISends via dedicated IPs

Prospect's InboxEmail from sarah@acme.com

Reply Path

Replies routed through SuperSend

Prospect Hits ReplyReply-to points to SuperSend

SuperSend Mail ServerCatches via MX routing

Unified InboxThreaded, categorized, actionable

Full conversation thread — outbound + replies — in one place

Built for Scale, Down to the Details

Send-As Architecture

One API key powers thousands of unique sending identities. Each has its own email, name, limits, and history. Zero marginal cost per sender.

Automated DNS Setup

SPF, DKIM, DMARC, Return Path, and MX records — all configured automatically when you purchase domains through SuperSend.

Per-API-Key Rate Limiting

Redis-backed rate limiting ensures you never exceed your Mission Inbox API limits. Auto-resets every 60 seconds.

Conversation Threading

In-Reply-To, References, and Thread-ID headers match every reply to the original outbound. Full conversation history preserved.

AI Reply Categorization

Every reply is auto-classified: interested, meeting request, not interested, out-of-office, unsubscribe. Contact status updates automatically.

Domain Health Monitoring

SPF, DKIM, DMARC, MX, and blacklist status tracked per domain. One-click fix guidance when something needs attention.

What No Other Tool Can Do

Traditional sequencers cap at mailbox scale. Transactional APIs can’t handle replies. SuperSend + Mission Inbox does both.

Capability	SuperSend+ Mission Inbox	Traditional SequencersApollo, Instantly, etc.	Transactional APIsSendGrid, Mailgun
Send millions per month
Multi-mailbox experience
Unified inbox with replies
Conversation threading
No mailbox purchasing needed
Dedicated IP infrastructure
Automated IP warm-up
Campaign sequences
AI reply categorization

Official Integration Partner

The Only Infrastructure Built for Cold Email at Scale

Mission Inbox is the only provider that builds dedicated, high-volume email sending infrastructure specifically for cold outreach. SendGrid, Mailgun, and Amazon SES explicitly prohibit cold email and will shut you down.

Mission Inbox provides the sending cube, dedicated IPs, automated warm-up, and domain management. SuperSend provides the sequencing, reply handling, conversation threading, and unified inbox. Together, they’re the complete high-volume cold email stack.

Talk to us about high-volume sending

What Mission Inbox Provides

Dedicated Sending Cube

Your own private mail server infrastructure

Dedicated IP Addresses

Scaled to your volume — more sends, more IPs

Automated IP Warm-Up

Gradual volume increase handled automatically

Domain Authentication

SPF, DKIM, Return Path records generated

Single OBM API Key

One key unlocks your entire infrastructure

What SuperSend Adds

Thousands of Sending Identities

Virtual send-as on one API key

Full Reply Handling

MX routing + webhook + conversation threading

Unified Inbox

Every reply across every sender in one place

AI Categorization

Bounce + reply intent classification

Not at high volume yet? SuperSend grows with you.

SuperSend also supports Google Workspace, Microsoft Outlook, and standard SMTP. Start with traditional mailboxes and scale into Mission Inbox OBM when your volume demands dedicated infrastructure. Same platform, same inbox, same workflows — just a different backend.

Google WorkspaceMicrosoft OutlookCustom SMTPMission Inbox OBM

FAQs

Common questions about high-volume sending with Mission Inbox OBM.

Mission Inbox is the only infrastructure provider that builds dedicated, high-volume email sending specifically for cold outreach. Their OBM (Outbound Mail) engine provides dedicated IP addresses, automated warm-up, and domain management — all accessed through a single API key. Unlike SendGrid, Mailgun, or Amazon SES, Mission Inbox explicitly supports cold email and will not shut you down for outbound prospecting.

SuperSend operates its own dedicated mail server. When an outbound email is sent via Mission Inbox, the reply-to header points to a mailbox on SuperSend's mail server. When a prospect replies, the reply routes through DNS (MX records) to SuperSend's server, which catches the email, matches it to the original outbound via threading headers (In-Reply-To, References, Thread-ID), and presents it in the unified inbox — fully threaded with the original conversation.

There is no hard limit. One Mission Inbox OBM API key can power thousands of unique sending identities in SuperSend. Each identity has its own email address, display name, daily limits, campaign assignments, and conversation history — but they all send through the same API. The marginal cost of adding a new identity is zero.

Not for high-volume sending through Mission Inbox OBM. The API key replaces the need for individual mailboxes entirely. However, SuperSend also supports Google Workspace, Outlook, and standard SMTP for teams that prefer traditional mailboxes or are starting at lower volume.

For domains purchased through SuperSend, the entire DNS setup — SPF, DKIM, DMARC, Return Path, and MX records — is automated. SuperSend registers the domain with Mission Inbox, pushes all DNS records to Cloudflare, and triggers verification. For bring-your-own domains, SuperSend provides the exact DNS records to configure.

Mission Inbox handles IP reputation and warm-up on their side. SuperSend adds AI bounce categorization, automated placement testing, domain health monitoring, and sender health scores on top. Bounces from Mission Inbox are processed via webhook and categorized automatically — hard bounces suppress the contact, rate limits adjust the sender automatically.

See High-Volume Sending in Action

Book a demo to see how SuperSend + Mission Inbox powers thousands of senders with full reply handling from a single API key.

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Join 500+ teams sending with SuperSend

Send Millions. Catch Every Reply.