How to Monitor Email Deliverability: Tools and Setup (2026)

By Rahul LakhaneyPublished on: Mar 31, 2026 · 8 min read · Last reviewed: Mar 2026

InboxKit Email Insights monitoring — Email Insights: real-time monitoring of 858 mailboxes with health status, sent/received counts, reply rates, and bounce rates.

InboxKit Inbox Placement Tests — Inbox Placement Tests: 8.3/10 average score, 82.7% inbox rate, test history with per-provider breakdown.

InfraGuard domain protection — InfraGuard: 24/7 domain monitoring including blacklist checks, DNS health, and unlimited inbox placement tests.

TL;DR

Flying blind on deliverability is the most expensive mistake in cold email. Here is how to set up monitoring with free tools (Google Postmaster, Microsoft SNDS) and InfraGuard for complete visibility.

The Monitoring Stack You Need

Complete deliverability monitoring requires multiple tools because no single tool covers everything.

Tool	What It Monitors	Cost	Coverage	Setup Time	Source
Google Postmaster Tools	Gmail-specific reputation, spam rate, auth	Free	Gmail only	15 min	postmaster.google.com
Microsoft SNDS	Microsoft-specific reputation, spam traps	Free	Outlook/Hotmail only	15 min	sendersupport.olc.protection.outlook.com
InboxKit Email Insights	Per-mailbox health, reply/bounce rates	Included	All providers (via IMAP)	0 (automatic)	app.inboxkit.com
InboxKit Inbox Placement	Actual inbox vs spam placement	Wallet-based per test	70+ seed addresses	5 min per test	app.inboxkit.com
InfraGuard	Blacklists, DNS health, continuous IPT	Per-domain subscription	50+ blacklists + DNS	2 min per domain	app.inboxkit.com
MXToolbox (free tier)	Basic blacklist + DNS check	Free (basic)	Manual checks only	1 min per check	mxtoolbox.com

Minimum viable monitoring: Google Postmaster + Microsoft SNDS + InboxKit Email Insights. These three cover Gmail reputation, Microsoft reputation, and per-mailbox health across all providers.

Recommended monitoring: Add InfraGuard for continuous blacklist monitoring and unlimited inbox placement tests. This catches problems hours before they affect campaign performance.

Source: Each tool's official documentation. InboxKit features from app.inboxkit.com.

Setting Up Google Postmaster Tools

Google Postmaster Tools is the single most important free monitoring tool for cold email.

Setup steps:

Step	Action	Time	Notes
1	Go to postmaster.google.com	1 min	Sign in with any Google account
2	Click 'Add Domain'	30 sec	Enter your sending domain
3	Verify ownership via DNS TXT record	5-10 min	Add the provided TXT record to your DNS
4	Wait for data (24-48 hours)	Wait	Need to send 100+ emails to Gmail first

What you can monitor:

Dashboard	What It Shows	Action Threshold	Source
Domain Reputation	High/Medium/Low/Bad rating	If Low or Bad: pause and investigate	Google Postmaster docs
Spam Rate	% of emails marked as spam by recipients	>0.1%: warning. >0.3%: critical	Google sender guidelines
IP Reputation	Reputation of sending IPs	Less relevant for Google Workspace users	Google Postmaster docs
Authentication	SPF/DKIM/DMARC pass rates	Should be 100%. Any failures need fixing	Google Postmaster docs
Encryption	TLS usage rate	Should be 100%	Google Postmaster docs
Delivery Errors	Bounce/rejection reasons	Any increase needs investigation	Google Postmaster docs

Limitation: Google Postmaster only shows data after you have sent enough volume to Gmail addresses (typically 100+ emails). Small-scale senders may not see data.

Source: Google Postmaster Tools documentation (support.google.com/mail/answer/9981691).

Setting Up Microsoft SNDS

Microsoft Smart Network Data Services monitors your reputation for Outlook, Hotmail, and Live.com recipients.

Setup steps:

Step	Action	Time
1	Go to sendersupport.olc.protection.outlook.com	1 min
2	Sign in with Microsoft account	1 min
3	Request access for your sending IPs	2 min
4	Verify IP ownership (automated)	5-15 min

What SNDS monitors:

Metric	Green (Good)	Yellow (Warning)	Red (Bad)
Spam rate	<0.1%	0.1-0.5%	>0.5%
Trap hits	0	1-5 per day	>5 per day
Complaint feedback	<0.05%	0.05-0.1%	>0.1%

Limitation: SNDS works at the IP level, not domain level. For Google Workspace and Microsoft 365 users, you are on shared IPs, so SNDS data may not be individually actionable. Domain reputation (via Google Postmaster) is more useful for cold email.

Source: Microsoft SNDS documentation (sendersupport.olc.protection.outlook.com/snds/FAQ.aspx).

InboxKit Monitoring Features

InboxKit provides three layers of monitoring, each solving different problems:

Layer 1: Email Insights (included with all mailboxes)

Metric	What It Tracks	Alert Threshold	Screenshot
Emails Sent (7d)	Volume per mailbox per week	Sudden drops = possible suspension	email-insights.png
Emails Received (7d)	Incoming volume	Low = possible deliverability issue	email-insights.png
Reply Rate	Percentage of sends getting replies	<5% for warmed mailbox = investigate	email-insights.png
Bounce Rate	Hard + soft bounces	>2% = clean lists immediately	email-insights.png
Health Status	Composite health score	Anything below Healthy = action needed	email-insights.png

Layer 2: Inbox Placement Tests (wallet-based)

Feature	Details
Seed addresses	70+ across Gmail, Microsoft, Yahoo, Apple Mail, corporate
Score	0-10 scale (8.3 average across InboxKit accounts)
Breakdown	Per-provider inbox vs spam vs missing
Cost	Wallet-based, per test
Frequency	Run before campaigns, weekly for active domains

Layer 3: InfraGuard (per-domain subscription)

Feature	Details
Blacklist monitoring	50+ blacklists checked continuously
DNS health	Monitors SPF/DKIM/DMARC for configuration drift
Unlimited IPT	Run inbox placement tests anytime at no extra cost
Alerts	Email/dashboard notifications on issues

Source: InboxKit app (see screenshots above). All three features visible in the dashboard.

Monitoring Schedule: What to Check and When

A practical monitoring schedule for cold email teams:

Frequency	What to Check	Tool	Time Required
Daily	Email Insights health status	InboxKit dashboard	2 min
Daily	Bounce rate per mailbox	Email Insights	2 min
Weekly	Google Postmaster reputation	postmaster.google.com	5 min
Weekly	Spam rate trend	Google Postmaster	3 min
Weekly	Run inbox placement test	InboxKit IPT	5 min
Monthly	Full blacklist check (manual)	InboxKit Blacklist Checker	5 min per domain
Continuous	Blacklist + DNS monitoring	InfraGuard (automated)	0 min (automated alerts)
Per campaign	Pre-send inbox placement test	InboxKit IPT	5 min

Total weekly time: 15-20 minutes for manual checks. InfraGuard automates the rest.

What to do when you find issues:

Issue	Severity	Immediate Action	Resolution Time
Bounce rate >5%	Critical	Pause sending, clean lists	1-2 days
Spam rate >0.3%	Critical	Pause campaigns, review targeting	1-2 weeks
Blacklisted (Spamhaus)	Critical	Stop sending, request removal	1-3 days
IPT score <6/10	Warning	Check authentication, review content	3-7 days
DKIM/DMARC failing	Warning	Fix DNS records	1-24 hours
Health status 'Needs Attention'	Warning	Review specific mailbox metrics	1-2 days

Source: InboxKit operational best practices, Google sender guidelines (support.google.com/mail/answer/81126).

Frequently Asked Questions

Google Postmaster Tools for Gmail reputation. It is free and shows your domain reputation, spam rate, and authentication pass rates. Set it up first. Source: postmaster.google.com.

Weekly for active domains, and before launching new campaigns. InfraGuard subscribers get unlimited tests. Without InfraGuard, run tests on your highest-volume domains.

Above 2% is a warning. Above 5% is critical. pause sending immediately and clean your lists. InboxKit Email Insights shows bounce rates per mailbox in real-time.

No, they complement each other. Google Postmaster shows Gmail-specific reputation data that only Google provides. InfraGuard monitors blacklists, DNS health, and runs inbox placement tests. Use both.

15-20 minutes per week for manual checks. InfraGuard automates blacklist and DNS monitoring, so most issues are caught automatically via alerts.