Updated September 4, 2026

TL;DR: An email deliverability monitoring tool tracks whether your emails reach the inbox: inbox placement, blacklist status, sender reputation, authentication, and spam complaints, ideally with real-time alerts. The best fit depends on your setup: Instantly.ai if you already send cold email through it, GlockApps or MxToolbox for affordable diagnostics, Validity Everest or Litmus for enterprise seed-list depth, SendForensics for deep analysis at a fair price, and Mailtrap for developers. High-volume senders should prioritize 24/7 blacklist and reputation alerts.

Deliverability is a focal point of every email marketing campaign, whether it's cold sales, lead nurturing, promotional emails, or newsletters. That’s why it’s arguably the most crucial email marketing metric to track. 

How you set up domains, warm-up sending accounts, write email copy, and choose leads directly affects email deliverability. To accurately monitor deliverability, you need email deliverability monitoring tools that give insight into all these metrics, ideally in real time. For the wider playbook on reaching the inbox, see Instantly’s guide to hitting 90%+ cold email deliverability.

Different types of email deliverability monitoring tools

While email deliverability tools share the common goal of getting your emails into inboxes, they tackle the problem from different angles depending on your use cases and marketing workflow.

Let's take a look.

Pre-send testing tools

These focus on catching issues before you hit send. Tools like Litmus, GlockApps, and SendForensics let you test individual emails against spam filters, preview rendering across devices, and analyze content for spam triggers.

Warm-up & reputation management tools

Dedicated to building and repairing sender reputation through automated engagement. Folderly, Warmy.io, and InboxAlly use networks of real accounts to interact with your emails and train ISPs that your mail is valuable. 

Infrastructure & compliance monitoring

Technical tools that monitor the health of your sending infrastructure. MxToolbox, Google Postmaster Tools, and Validity Everest's compliance features track DNS records, authentication protocols, blacklist status, and adherence to Gmail or Yahoo email marketing requirements. 

All-in-one platforms

Combine sending, warm-up, and monitoring in a single platform. Tools like Instantly and Mailtrap integrate deliverability checks directly into your campaign workflow. Both also have great API support for teams with developers.  

Enterprise analytics suites

Comprehensive platforms with competitive benchmarking, multi-domain monitoring, and white-label reporting. Validity Everest, MailMonitor, and enterprise tiers of Litmus offer the deepest seedlist coverage and analytics. 

What is a seed list in deliverability monitoring?

If you’re looking into email deliverability monitoring tools, one of the most common terms you’ll encounter is seed lists. These are a collection of test email addresses spread across different email service providers (ESPs). 

Email deliverability monitoring tools send sample emails to their seed lists and report where your message lands (spam, promotions, or the primary inbox). So instead of testing on actual leads, you can do so safely and adjust email copy before the real campaign starts. For a step-by-step on running these checks, see how to test your email deliverability.

The 9 best email deliverability monitoring tools compared

Here is how the nine tools compare on what they monitor, who they suit, and price. Details on each follow below.

Honest note: Instantly's monitoring lives inside its cold-email workflow, so it is the natural pick if you already send from Instantly. If you need standalone monitoring across multiple ESPs or the deepest enterprise seed-list coverage, Validity Everest or Litmus go further.

Instantly: best email deliverability monitoring tool for cold email

Instantly integrates email deliverability monitoring into the cold email workflow. Even without a paid Inbox Placement plan, you get 2 free inbox placement tests that check where your emails land (inbox, promotions, or spam).

The platform also provides accurate spam filter scores, blacklist status, authentication checks (SPF, DKIM, DMARC), and content analysis for spam triggers.

If you do get the Inbox Placement plans, you gain access to unlimited testing to track deliverability across every campaign.

What's more, the Growth plan includes Analytics to track campaign performance (open, click, and reply rates), and Copilot, via Instantly Credits, for campaign research and creation. Deliverability-specific monitoring and fixes come from the Deliverability AI Agent on Hyper Growth and above.

Key features:

• Tests where your emails land (inbox vs promotions vs spam)
• Spam filter scores and content insights
• Monitors 94 blacklists for your IPs and domains
• Offers AI recommendations to improve email copy
• Shows detailed deliverability per sending account
• Campaign-Level Deliverability Checks
• Built-in deliverability scoring in the sequence editor
• Preview and check deliverability scores before sending
• Advanced Infrastructure Monitoring
• SISR (dedicated, private IP pools with rotation) on Light Speed and above
• Continuous IP reputation monitoring
• Proactive removal of blacklisted IPs

Pricing: All users get 2 free tests to start. 

• Growth Inbox Placement: $47/month or $451/year. Unlimited one-time tests.
• Hypergrowth Inbox Placement: $97/month or $931/year. Unlimited one-time tests + Automated tests

GlockApps: the affordable all-rounder for SMBs and agencies

GlockApps has been on the market for over a decade. It's affordable and fits right into the email marketing stack for small businesses. The only caveat is that GlockApps mainly has seed lists in the US, which is a downside if you're targeting UK providers like BT, Virgin, and Sky.

GlockApps combines content analysis and inbox placement. It’s one of the best tools for sending out high-volume newsletters or nurturing emails. You get an HTML checker, spam content detection, and the ability to detect elements that trigger filters. 

Key features:

• Spam filter scoring against Google, Barracuda, and SpamAssassin
• Full DMARC Analyzer (with 10,000 free DMARC messages/month)
• Blacklist monitoring across 50+ blocklists
• IP reputation tracking
• HTML content checking
• Gmail tab prediction (Primary vs. Promotions)
• API 2.0 access
• Notifications via Email, Slack, or Telegram
• Shareable PDF reports with white-label options for agencies

Pricing: Starts with a free plan offering 2 spam test credits per month:

• Essential: $85/month. Includes 30 spam test credits and unlimited DMARC domains.
• Growth: $142/month. Includes 90 spam test credits, 5 users, unlimited DMARC domains and 100,000 DMARC messages.
• Enterprise: $185/month. Includes 150 spam test credits, 10 users, 1,000,000 DMARC messages and 9 DMARKOFF domains.
• Standalone credit packs are available from $16.99 for 3 tests.

MxToolbox Delivery Center: an infrastructure first diagnosis

MxToolbox has been the go-to free DNS diagnostic tool for IT professionals for nearly three decades. The paid Delivery Center extends those capabilities into DMARC deployment, inbox placement analysis, and comprehensive blacklist monitoring.

However, the interface is dated. There’s also a 5-domain limit. So, it might not be ideal if you’re scaling outreach or have multiple domains. MxToolbox does make up for it with its infrastructure-first diagnostics.

It's built for IT administrators and technical teams who need strong DNS health monitoring, guided DMARC deployment to reject policy, and the industry's most extensive blacklist coverage of 100+ lists. 

Key features:

• Monitoring against 100+ blacklists (free tier covers top 30)
• Guided DMARC deployment to reject policy
• Adaptive blacklist monitoring that auto-detects all senders
• Inbox placement analysis with MxTips improvement suggestions
• SPF flattening
• Domain impersonation protection
• BIMI record analysis

Pricing: Offers a free plan with weekly blacklist monitoring for one website:

• Delivery Center: $129/month. Includes inbox placement, DMARC guidance, up to 5 domains.
• Delivery Center Plus: $399/month. Adds adaptive blacklist monitoring, SPF flattening, impersonation protection, and dedicated expert support.
• Managed email delivery services available at custom pricing with a 30-day satisfaction guarantee.

Validity Everest: built for enterprise seed-list depth

Validity Everest combines three major names in the deliverability space: Return Path, 250ok, and BriteVerify. Between them is over 20 years' worth of high-quality industry data. They also claim to have the largest global seed list of any deliverability tool. 

Key features:

• Inbox placement testing with competitive benchmarking
• Largest global seedlist covering 100+ webmail and hosting providers
• Real-time sender reputation monitoring across shared and dedicated IPs
• Spam trap and complaint tracking
• Built-in BriteVerify email verification
• DKIM/SPF/DMARC/BIMI authentication monitoring
• Audience engagement insights (open times, device types, dwell times)
• Integrations with Mailgun, SendGrid, Amazon SES, and Salesforce Marketing Cloud

Pricing: Validity doesn't publish pricing publicly. Plans are tiered, with the entry level limited to a small number of inbox placement tests and no spam checking, and higher tiers unlocking engagement analytics, ESP integrations, and API access. Enterprise pricing is custom quote only. Contact their sales team for current rates.

Litmus: premium pre-send testing

Litmus was founded in 2005 and grew to serve 700,000+ marketing professionals, including 80% of the Fortune 100, as the industry's leading email testing platform. Validity acquired Litmus in April 2025, combining its pre-send optimization strengths with Validity's post-send analytics.

What Litmus brings to the table is comprehensive pre-send QA. You get email previews across 100+ email clients, spam filter testing against 25+ filters, and engagement analytics showing whether emails were deleted, glanced at, or read. 

Key features:

• Spam filter testing against 25+ filters
• Email previews across 100+ email clients and devices (including Dark Mode)
• DKIM/SPF/DMARC/BIMI authentication monitoring
• Blocklist monitoring against 60+ blocklists (Enterprise tier)
• Email Guardian for 24/7 rendering change alerts
• Deep ESP integrations with Salesforce Marketing Cloud, Oracle Eloqua, Marketo, HubSpot, Mailchimp, Klaviyo, and Adobe Campaign

Pricing: Litmus pricing starts at $1,500/month for the Foundation plan, with Growth and Scale available by custom quote. There is no free plan.

SendForensics: deep deliverability analysis at accessible pricing

SendForensics doesn’t cut corners. All plans include all core features. The tiers only differ by volume limits (domains, users, DMARC reports). You get unlimited inbox placement tests on every plan, with fair use capped at 50 seedlist tests per domain per month. 

Despite the limitations, you still get deep deliverability analysis using machine learning. Their proprietary Email Deliverability Score (EDS) goes beyond standard spam testing to analyze individual content components. 

Key Features:

• ML-powered spam testing with proprietary Email Deliverability Score (EDS)
• Unlimited inbox placement tests on all plans (fair use: 50 tests/domain/month)
• DMARC monitoring with auto-generated starter records
• Real-time blacklist checking
• 360-degree reputation dashboard integrating Google Postmaster Tools and Microsoft SNDS data
• 24/7 infrastructure monitoring with Slack/email alerts

Pricing: Annual billing saves 20%. Non-profit discounts available.

• Brand: $49/month. Includes 2 domains, 2 users, 100K DMARC reports
• Company: $79/month. Includes 5 domains, 5 users, 1M DMARC reports
• Agency: $199/month. Includes 15 domains, 10 users
• Enterprise: Starting at $349/month. Includes 30 domains, 20 users
• Add-on domains and users cost $8–10/month each

Mailtrap: the developer's deliverability platform

Mailtrap started because the team behind it accidentally sent about 20,000 test emails to customers. To prevent that from happening again, they created an internal tool that became a full email deliverability platform with over 150k monthly users, including PayPal and Adobe. 

If you’re working with a developer, Mailtrap gives tools for email testing with production sending. It's built for product companies and SaaS teams who need both a safe sandbox environment (so test emails never reach customers) and production delivery with built-in monitoring.

Key features:

• Email API/SMTP with SDKs in 12 languages
• Dedicated IPs with automatic warm-up
• Email Sandbox that captures test emails safely
• HTML/CSS validation
• SpamAssassin scoring
• SPF/DKIM/DMARC checks
• Real-time analytics tracking delivery rates, bounce rates, and spam complaints
• ISP-level engagement breakdowns
• Free blacklist/SPF/DKIM checker tools

Pricing: Volume-based (not per-contact). Annual billing saves 20%.

• Free: 4,000 emails/month
• Basic tiers: $15/month (10K emails, 5 domains)
• Business plans: $85/month. Includes dedicated IP, auto warm-up, 100 domains, 24/7 priority support
• Enterprise: $750/month

Folderly: AI-driven deliverability for sales teams

Folderly is built specifically for B2B sales teams and lead-generation agencies running cold-email campaigns at scale. It uses AI-driven warm-up with human-like engagement patterns to repair and maintain the sender's reputation. 

The main downside is that the pricing model can get expensive for small teams. But the pricing drops sharply at higher volumes. 

If you’re already sending emails in bulk, Folderly can pair your deliverability system with AI-powered monitoring and repairs. You get a real time Folderly Score, daily inbox vs. spam placement tracking, and spam trigger detection with color-coded content analysis.

Key features:

• AI-driven email warm-up with human-like engagement patterns
• Real time Folderly Score (0-100 deliverability metric)
• Daily inbox vs. spam placement tracking
• Spam trigger detection with color-coded content analysis
• DNS configuration support (SPF, DKIM, DMARC, BIMI)
• Gmail and Outlook-specific spam reason detection
• Inbox Insights product for placement testing and IP reputation overview

Pricing: Per-mailbox model. All tiers include full feature access.

• Free: includes 60 monthly credits
• Starter: $49/month, includes 150 monthly credits, email support, and single-email generation
• Growth: $199/month, includes 1,000 monthly credits, higher-volume generation and priority support
• Pro: $499/month, includes 2,500 monthly credits, account-managed API and webhook access, advanced integration planning and billing and usage support
• Agency: $1,499/month, includes 5,000+ monthly credits, multi-client generation volume, custom onboarding, and folderly deliverability handoff

InboxAlly: best for repairing sender reputation

InboxAlly is getting a lot of hype in the cold outreach space, even winning G2 Winter 2026 High Performer status. While it's not cost-effective for scaling deliverability across large teams, it does a great job repairing the sender reputation of previously high-performing inboxes.

Unfortunately, it’s not the best tool for smaller teams. Pricing starts at $149/month and only covers one sending account. The Jump to the next tier is at $645/month for 5 accounts. It also doesn’t have native integrations with platforms like Salesforce or SendGrid. 

What InboxAlly does best is engagement-driven reputation repair. Rather than just testing where emails land, it uses a network of real seed accounts that actively engage with your emails by opening them, clicking links, marking them as important, and moving them out of spam.

Key features:

• Engagement-based warm-up with customizable interaction profiles
• Inbox placement testing across Gmail, Yahoo, Outlook, Hotmail, and Google Workspace
• Real-time 30-day placement tracking
• Broadcast auto-detect for campaigns
• Multiple sender profile management
• Free tools (email content tester, spam checker, blacklist lookup)
• DMARC analytics dashboard
• SPF/DKIM/DMARC auditing

Pricing: Flat monthly rates. 10-day free trial with no credit card required.

• Starter: $149/month. Includes 100 daily seed emails, 1 sender profile
• Plus: $645/month. Includes 500 daily seeds, 5 profiles
• Premium: $1,190/month. Includes 1,000 daily seeds, 10 profiles, phone support, and weekly strategy sessions
• Enterprise: Custom pricing

Frequently asked questions about email deliverability monitoring

What is the best email deliverability monitoring tool?

It depends on your setup. Instantly is best if you already send cold email through it, since monitoring is built in. GlockApps and MxToolbox are the affordable diagnostic picks, Validity Everest and Litmus suit enterprise seed-list depth, and SendForensics offers deep analysis at a fair price. Match the tool to your sending platform and volume.

Is there a free email deliverability monitoring tool?

Yes, several offer free tiers: MxToolbox gives weekly blacklist monitoring for one site, GlockApps includes two spam-test credits a month, Mailtrap has a free plan, and Instantly includes two free inbox placement tests. Free tiers cap volume and features, so they suit spot-checks rather than continuous monitoring.

What should an email deliverability monitoring tool track?

At a minimum: inbox placement (inbox vs spam vs promotions), blacklist and blocklist status, sender reputation, SPF, DKIM, and DMARC authentication, and spam-complaint rate. For high-volume sending, real-time or 24/7 alerts on blacklists and reputation matter most, since they catch a problem before it spreads.

Do high-volume senders need 24/7 monitoring?

Yes. At volume, a blacklisting or reputation drop can burn a domain within hours, so real-time alerting pays for itself. Tools like SendForensics and Litmus (Email Guardian) offer 24/7 alerts. For low-volume sending, periodic checks are usually enough.

Key takeaways

Businesses and agencies that want to scale email marketing need a system to ensure high email deliverability. A key part of this system is an email deliverability monitoring tool built around your needs. To recap, here are the tools we recommend:

• Instantly.ai: Best for scaling cold email marketing. Everything you need under one roof.
• GlockApps & MxToolbox: Affordable deliverability monitoring focusing on diagnostics.
• Everest & Litmus: Premium-priced tools best for enterprises that need global seedlists.
• SendForensics & Mailtrap: AI-driven diagnostics. Mailtrap: developer-focused features (API, sandbox).
• Folderly & InboxAlly: For repairing the deliverability of previously high-performing domains.  

If you want your entire email stack in one platform, Instantly has you covered. Get domains, warm-up accounts, buy leads, automate personalization and outreach, and monitor deliverability as you scale. Try Instantly for free today.