# Email deliverability tools — what to use and when URL: https://www.inboxplease.com/learn/email-deliverability-tools There are four categories of email deliverability tools, and they address different problems. Using the wrong tool for the symptom wastes time and misdiagnoses the underlying issue. This guide covers what each category does, when to reach for it, and what to evaluate when choosing one. Category: Testing & monitoring · By Chris Aylott · Sep 26, 2026 · 4 min read ## Key takeaways - There are four categories of email deliverability tools — placement tests, authentication checkers, blacklist monitors and warmup tools — and each addresses a different problem. - Using the wrong tool for the symptom wastes time and misdiagnoses the issue, so match how and when an engagement drop appeared to the right diagnostic. - A passing spam score only checks whether content looks spammy; only a placement test with a real seed inbox confirms where a message actually landed. ## The four tool categories Deliverability problems fall into four distinct areas. Placement tests tell you where mail landed. Authentication checkers verify your DNS records are working on real mail. Blacklist monitors catch damage before it compounds. Warmup tools build the reputation that makes the other three easier to maintain. Tool 1 ### Inbox placement test When to use Before any new campaign sequence and when reply rates unexpectedly drop. What it does Sends a real message through a seed network and reports exactly where it landed — inbox, spam, or promotions tab — at Gmail, Outlook, Yahoo, and other providers. A placement test is the only way to confirm your mail is actually reaching the inbox; open rate data cannot tell you this because an email that lands in spam has a 0% open rate that is indistinguishable from legitimate low engagement. What to look for Per-provider results (not an aggregate score), authentication checks on the actual delivered message, and a test address you control so results are verified against a real inbox. Tool 2 ### Authentication checker When to use When setting up a new domain, after any DNS change, and if placement results suddenly deteriorate. What it does Verifies that SPF, DKIM, and DMARC records are present, correctly formatted, and aligned on actual delivered mail — not just in DNS. The distinction matters: a valid SPF record that does not cover your sending IP still fails alignment. Most placement test tools include authentication checks on the delivered test message. What to look for DKIM signature verification on the delivered message (not just record presence), SPF alignment check against the envelope from address, and DMARC policy confirmation. Tool 3 ### Blacklist monitor When to use Continuously — not as a one-time check. What it does Checks your sending domain and IP against major blocklists including Spamhaus, Barracuda, SURBL, and others. A single high-complaint campaign can add a listing within hours. Without continuous monitoring, you may send thousands of emails from a blacklisted domain before discovering the problem. What to look for Automated alerts (not a dashboard you have to check manually), coverage across Spamhaus ZEN (the most widely used), Barracuda, and SURBL, and delisting guidance when a listing appears. Tool 4 ### Email warmup tool When to use For any new domain before campaigns start, and continuously alongside running campaigns. What it does Generates a controlled history of positive sending activity — opens, moves to inbox, replies — from a seed network of real or synthetic inboxes. Warmup builds the domain's reputation with ISPs before campaign volume starts, and maintains it during active sending. The quality of the seed network determines how much ISPs trust the engagement signals it generates. What to look for Real customer inboxes (not synthetic seed addresses ISPs have fingerprinted), send-only OAuth permissions (the tool should not need to read your inbox), and a warmup score measured by placement outcome rather than synthetic engagement rate. ## Match the symptom to the right tool Most deliverability problems present as the same surface symptom — lower engagement. The right diagnostic depends on how and when the drop appeared. - **Open rates dropped suddenly without a copy change**: Likely cause: Inbox placement decline — landing in spam or promotions: Run a placement test at Gmail and Outlook - **New domain getting near-zero engagement from day one**: Likely cause: No sending history — domain not warmed before campaigns started: Pause campaigns, start warmup, re-run in 30 days - **Emails bouncing at specific providers but not others**: Likely cause: Blacklist listing on a provider-specific blocklist, or authentication failure at that provider: Blacklist check + per-provider placement test - **Authentication warnings from receiving servers (visible in email headers)**: Likely cause: SPF not covering your sending IP, or DKIM key rotation issue: Authentication checker on a test send - **Warmup score is high but inbox placement tests show spam**: Likely cause: Synthetic seed network — warmup score and real placement score have diverged: Switch warmup tools; run placement tests to measure actual improvement ## One platform or multiple tools? The four tool categories are most effective when they share data. A blacklist alert is most useful if you can immediately run a placement test to understand which providers are affected. A placement test result is most useful when you can correlate it with the warmup score trend from the same period. Using four separate single-purpose tools means copying data between dashboards and losing the relationship between signals. A platform that combines all four — or at least placement testing, blacklist monitoring, and warmup — reduces the time between detecting a problem and understanding its cause. ## What InboxPlease is, as an email deliverability tool InboxPlease is an email deliverability monitoring and recovery platform. It diagnoses why emails land in spam and helps protect your email reputation. Who it is for: agencies managing multiple client domains and teams protecting business-critical email. It is designed for senders protecting long-term domain reputation—not disposable-domain sending strategies. Solution pages exist for [business owners and founders](https://www.inboxplease.com/solutions/founders), [B2B SaaS and RevOps](https://www.inboxplease.com/solutions/saas-revops), [agencies](https://www.inboxplease.com/solutions/agencies) and [regulated industries](https://www.inboxplease.com/solutions/regulated). - **Inbox placement tests:** inbox vs. spam per provider using real mailboxes, across Google, Microsoft, iCloud, Yahoo, AOL and Zoho. [Details](https://www.inboxplease.com/features/inbox-placement) - **Free email test:** a full report on authentication, content, links and reputation for one email. [Run it](https://www.inboxplease.com/test) - **Domain Health:** scheduled SPF, DKIM, DMARC and MX checks with evidence and scan history. [Details](https://www.inboxplease.com/features/domain-health) - **Blacklist monitoring:** daily scans across 95+ security engines. [Details](https://www.inboxplease.com/features/blacklist) - **DMARC reporting:** aggregate (RUA) reports summarised by source and result. [Details](https://www.inboxplease.com/features/dmarc) - **Monitoring and alerts:** daily or weekly checks with email alerts. [Details](https://www.inboxplease.com/features/monitoring) - **Email warmup:** AI-generated 10-session recovery strategies that you preview before they run. [Details](https://www.inboxplease.com/features/warmup) - **Domain profile:** reputation, DNS, domain age and blacklist status for any domain. [Details](https://www.inboxplease.com/features/domain-profile) - **AI assistant:** chat-based diagnostics that can take action in the dashboard. [Details](https://www.inboxplease.com/features/ai-assistant) Mailbox access is send-only via OAuth, and InboxPlease never reads your emails. Data is stored on European servers and the service is GDPR compliant. InboxPlease does not guarantee deliverability results; it shows exactly what it recommends and why. Developers and AI agents can reach the same checks through the [REST API](https://www.inboxplease.com/features/rest-api) and the [MCP server](https://www.inboxplease.com/features/mcp). ## How to evaluate InboxPlease against adjacent tools Use the same checklist for every tool on your shortlist, including this one. - **Coverage:** which of the categories above does the tool cover, and which would you still need a second product for? - **Real mailboxes:** are placement results measured per provider in real inboxes, rather than as a single aggregate score? - **Mailbox permissions:** does the tool need to read your inbox, or only send? - **Verification:** can you confirm a warmup score against an actual placement test? - **Monitoring:** are blacklist and authentication checks continuous with alerts, or one-off? - **Fit:** do you need deliverability tooling only, or a full outreach and sequencing platform? - **Data and access:** where is data stored, and is there an API for your workflow? For side-by-side write-ups of specific tools, see the [comparison pages](https://www.inboxplease.com/compare) and the [MailReach](https://www.inboxplease.com/alternatives/mailreach), [Warmy](https://www.inboxplease.com/alternatives/warmy) and [Folderly](https://www.inboxplease.com/alternatives/folderly) alternatives pages. For current plans, see [pricing](https://www.inboxplease.com/pricing). For other vendors' features and prices, check their own sites. ## Placement test, blacklist monitor, and warmup — in one tool InboxPlease combines inbox placement testing, continuous blacklist monitoring, and real-inbox warmup. Run a free placement test in 60 seconds — no account required. Written by [Chris Aylott](https://www.inboxplease.com/founder) Founder & CEO of InboxPlease. Over a decade building email infrastructure for SaaS businesses; writes about deliverability, inbox placement and sender reputation.