Start Free Trial
From $49/mo — 14-day free trial, no card

Know why your inbox rate dropped — before it costs your revenue.

InboxStack watches every signal across Gmail, Outlook & Yahoo and flags what's worth a closer look, backed by a complete, timestamped history behind every alert. We do the watching. You make the call.

Check my domain now Run a free deliverability audit

Takes 60 seconds. No credit card required.

Who It's For

Built for every sender. Scaled for Marketing Agencies & ESP's.

Two audiences, one engine. Self-serve for senders. White-label-ready for the platforms that serve them.

For Email Senders

You built the list. Now get it to the inbox.

InboxStack Brain gives individual senders and marketing teams the same intelligence used by enterprise deliverability engineers — without the complexity or the Validity price tag.

  • Know your deliverability health score before you hit send — not after the campaign underperforms
  • Plain-English explanations of exactly what's hurting your inbox rates and how to fix it
  • Monitor reputation across Gmail, Yahoo, Outlook, and Apple Mail from a single dashboard
Start free — no credit card
For Agencies & ESPs

Your customers expect inbox. Brain makes sure they get it.

ESPs and agencies live and die by deliverability. InboxStack Brain lets you monitor every customer domain at scale and act before your customers notice a problem.

  • Surface deliverability incidents across your entire customer base with zero manual overhead
  • Arm your support team with root cause analysis and fix playbooks before tickets are filed
  • White-label Brain intelligence as a platform differentiator — your brand, our engine
Talk to our ESP team

Customer Results

See what serious senders say about Brain.

Not generic praise — specific incidents caught and resolved.

Optin Secure

InboxStack Brain flagged a reputation issue before it hit inbox rates. The RCA Inspector pointed straight to the problem and we fixed it the same morning — without paging an engineer.
Joe Castelli
CEO · Optin Secure

Campaign Studio

The Causal Graph shows us exactly what broke and why. Our clients see better inbox rates and we spend far less time firefighting deliverability across the agency portfolio.
Abhinav Dixit
Founder · Campaign Studio

Orbosys

The Signal Engine caught an SPF issue that was silently tanking our Outlook delivery — we'd never have spotted it ourselves. Brain told us why it was happening and exactly what to fix.
Kunal Srivastava
Founder · Orbosys

How It Works

From first signal to final fix — automatically

No log diving. No spreadsheet exports. No deliverability consultant on retainer. Brain handles the diagnosis end-to-end.

Step 01

Connect your ESP in 5 minutes

Plug in your ESP via API or webhook. Brain starts pulling live performance signals immediately and establishes your baseline across every MBP.

Step 02

Brain detects & diagnoses

When a signal deviates, the RCA Inspector automatically builds a causal graph. Authentication failures, reputation events, and provider-specific rejections map to a clear verdict in under 4 minutes.

Step 03

A specific fix — not a checklist

The Resolution Center translates the causal graph into a prioritized playbook built for your exact situation. Execute the fix — Brain confirms the recovery.

The Problem

The old way of monitoring email is broken

Most tools tell you something is wrong. They show you a red light. No context. No cause. No plan. No fix.

Inbox rate crash — placeholder

Your inbox rate crashed 22% and you had no idea until Monday

Most platforms flag failures hours or days after they begin — by then, the damage is done.

Black-box dashboard — placeholder

You know something is wrong. You don't know what. Or why.

Without causal context, every investigation is a shot in the dark costing days of engineering time.

Per-MBP disagreement — placeholder

Gmail says one thing. Outlook says another. Yahoo says nothing.

Each provider rejects for different reasons — fixing one without knowing the cause can make the others worse.

Generic checklist — placeholder

Generic advice that doesn't apply to your specific situation

Advice disconnected from your actual infrastructure and sending history helps no one.

The Solution

One platform. Three jobs. Zero guesswork.

InboxStack Brain covers every phase of your deliverability workflow — before you send, when something breaks, and every day in between.

Before a Campaign

Pre-send confidence — every domain, every send.

What's included

  • Pre-send seed testing across Gmail, Outlook & Yahoo inboxes
  • Full domain health check: SPF, DKIM, DMARC, BIMI
  • Authentication audit with pass/fail diagnosis
  • Sending infrastructure fingerprint before every blast

During a Problem

Anomaly to root cause to fix in under 4 minutes.

What's included

  • ML Signal Engine detects anomalies before inbox rates move
  • Incident Intelligence classifies severity automatically
  • RCA Inspector traces the exact causal chain behind every failure
  • AI-generated resolution playbook tailored to your exact incident

Every Day

Hands-off hygiene that runs while you sleep.

What's included

  • Blacklist monitoring across 50+ lists (daily, not weekly)
  • DMARC report parsing and policy monitoring
  • Google Postmaster & Microsoft SNDS tracked automatically
  • Sender Score & IP reputation snapshots every 24 hours

Connectors & data sources

Your ESP. Postmaster. DMARC. All in one feed.

Brain pulls real performance data from your ESP — not the estimates competitors run on. Then we layer in Google Postmaster, Microsoft SNDS, DMARC reports, DNS audits, and 50+ blocklists. Every diagnosis runs on full evidence.

  • Google Postmaster
  • Microsoft SNDS
  • DMARC Reports
  • DNS Audit
  • 50+ Blocklists

See it in action

Plug Into Your ESP. Intelligence Starts Flowing in Minutes.

Signal Engine LIVE
24h 7d 30d
Inbox rate
94.2%↑ 2.1
Spam folder
3.1%↑ 0.4
Complaint
0.08%↓ 0.02
DMARC pass
99.6%↑ 0.1

Signal Engine

Know about reputation problems before your campaign does

Real-time anomaly detection across every send. Brain classifies the deviation, traces the causal chain, and surfaces the exact fix.

Daily Monitor LIVE
Gmail
96.1%
Outlook
93.8%
Yahoo
88.4%
Yahoo dip detected · stream_promo

Daily Monitoring

Per-provider delivery rates. Every day. Automatically.

Gmail, Outlook, and Yahoo broken out separately — per IP, per domain, per stream. Catch a Yahoo-only drop before anyone files a ticket.

War Room LIVE
acme.com
94.2%
newsletters.acme.com
96.1%
shop.acme.com
92.8%
alerts.acme.com
99.6%

Brain Intelligence

One command center. Every domain. Every incident. Live.

Multi-domain senders stop pivoting between dashboards. Every sending identity in a single live view, prioritized by revenue impact.

Pre-send Test READY
Gmail
Inbox
14 / 15
Outlook
Inbox
12 / 15
Yahoo
Promotions
9 / 15
Apple
Inbox
15 / 15
87% predicted inbox rate

Pre-send Seed Testing

Know your inbox rate before you hit send

Drop your draft into Brain. We seed-test across Gmail, Outlook, Yahoo, and Apple in seconds — and tell you exactly which providers will reject it before your audience does.

RCA Inspector LIVE 87% conf.
Causal chain · incident #4821
! Content fingerprint change detected tmpl_3f2a · +47%
! Spam corpus pattern match 0.81
✓ SPF alignment PASS
✓ DKIM & DMARC PASS
Top hypothesis 87% conf.
Content trigger — revert template tmpl_3f2a or rephrase CTA block

Root Cause Analysis

Brain tells you why — with evidence, not guesses.

Every diagnosis cites the signals it's based on: header changes, auth deltas, content fingerprints, list churn, IP warmup state.

<4 min
Average time from anomaly detection to root cause
50+
Blacklists monitored daily across all domains
8 ESPs
Native connectors: Mailchimp, SendGrid, SES, Brevo & more
22 yrs
Combined deliverability experience encoded in the Brain engine

Stop diagnosing fires.
Start preventing them.

Start free trial Talk to our team