Email Domain Reputation Checker: 6 Tools Compared

When well-written emails end up in spam, the cause is often your email domain reputation: the trust mailbox providers place in your sending domain, based on how you have sent in the past.

Checking it is how you find a deliverability problem before it shows up as missing replies. A domain reputation check draws on three kinds of data: the mailbox providers' own dashboards, score and blocklist lookups, and seed-list placement tests.

Why Your Domain Reputation Matters

Every campaign you send adds to your domain's history with Gmail, Outlook and Yahoo. Good history gets your mail into the inbox. Poor history gets it filtered, delayed or rejected.

Reputation is built from what recipients do with your mail. Consistent, wanted mail builds trust; bounces and spam reports erode it. A damaged reputation lowers the results of every campaign that follows.

What a Damaged Reputation Looks Like

The pattern is common: a team sends to an old segment full of inactive addresses, bounces and spam complaints jump, and the next campaigns land in spam at one or more providers. Opens and replies fall, even though the copy did not change.

That is why you monitor your reputation with an email domain reputation checker: to catch the drop after one bad send. For the broader practices behind a good reputation, see our email deliverability best practices.

Key Factors That Shape Your Score

Providers keep their filtering rules private, and some publish limits. Google asks senders to keep the spam rate below 0.1% and to "prevent spam rates from ever reaching 0.3% or higher" (Google).

• Sender authentication: SPF, DKIM and DMARC set up and passing; Gmail and Yahoo require all three from bulk senders (Google, Yahoo)

• User engagement: replies, opens and clicks show recipients want your mail

• Spam complaint rate: each "report spam" click is one of the strongest negative signals

• List hygiene: removing invalid and unengaged contacts keeps bounces low and avoids spam traps

Choosing Email Reputation Checker Tools

No single tool shows everything. Use a small set: the providers' own tools, a blocklist check and a placement test.

Start with the mailbox providers' tools. If any of your recipients use personal Gmail addresses, set up Google Postmaster Tools: it is Google's own data about your domain. If you send from IP addresses you control, Microsoft's Smart Network Data Services (SNDS) gives per-IP data for Outlook.com.

Free Tools Versus Paid Platforms

Provider tools show one provider each. Postmaster Tools tells you nothing about Outlook or Yahoo. Third-party platforms fill that gap. Services like GlockApps and Validity's Everest use a seed list: they send your email to test mailboxes at many providers and report where it landed: inbox, spam or a tab. Validity now sells Everest's placement testing as part of Validity Engage; the old Everest page redirects there.

Features That Matter

• Blacklist monitoring: alerts when your domain or IP appears on major blocklists such as Spamhaus, so you can react before the listing blocks more of your mail

• Inbox placement testing: where your mail lands at each provider; "inbox at Gmail, spam at Outlook" changes what you fix first

• Authentication checks: confirms SPF, DKIM and DMARC are published and passing

• History: a trend line lets you tie a drop to a specific campaign

Domain reputation follows your domain wherever you send from; IP reputation belongs to the server you send from, and the two can move independently. Sender Score is Validity's "free credit rating for your IP address, in the form of a score from zero to 100" (Validity); its lookup form also accepts a domain.

Comparison of Email Reputation Checkers

How to Check Your Domain With Google Postmaster Tools

Verify Your Domain

Add the domain you authenticate with: Google asks for "either the DKIM (d=) domain or the SPF (Return-Path) domain." Copy the TXT or CNAME record Google gives you into your DNS and click Verify. Verification is usually immediate, but Google says it "can take up to 10 minutes" (Google).

Two limits matter for cold email:

• "Data in Postmaster Tools only applies to messages sent to personal Gmail accounts," meaning addresses ending in @gmail.com or @googlemail.com; mail to Google Workspace business addresses does not show up

• "Data might be missing if the total number of messages for a given day is too low," so a domain that sends small volumes may show nothing

The Dashboards to Read

Google's Postmaster Tools dashboards page documents eight dashboards. These four are part of Postmaster Tools v2 and matter most for reputation:

Under Compliance status, the Deliverability analysis tool "provides a recommendation about your domain's status with Gmail." You get one, for example, when you send too little email, when messages fail to deliver or when you exceed the recommended spam threshold.

The delivery error reasons include "Sending domain has a low reputation", "Sending IP has a low reputation" and "Domain is in one or more public RBLs". For "Suspected spam", Google says: "Typically, this error is the result of a low domain or IP address reputation."

A low spam rate can hide a problem. Google describes this case: "Gmail is automatically sending a significant number of your messages to spam. The dashboard rate is low because recipients get fewer of your messages in their Inbox."

What Happened to the Domain Reputation Dashboard

The legacy interface still has the Domain Reputation and IP Reputation dashboards. They rate a domain or IP as High, Medium, Low or Bad; at Bad, mail is "almost always marked as spam or rejected by the receiving server."

Google's deprecation page says: "Thanks to helpful sender feedback, we're postponing the deprecation of the legacy Postmaster Tools web interface." The reputation dashboards are still going: "All the dashboards in old Postmaster Tools are available in v2, with the exception of the Domain and IP Reputation dashboards, which will be retired." The v1 API "will be retired" too. Google gives no date: "Stay tuned for more information on timing."

Google's reason: the dashboard "can be misleading as reputation is only one of many factors affecting deliverability." Read the grade while the legacy interface lasts, and build your monitoring on Compliance status, Spam rate and Delivery errors. More detail: what replaces the reputation dashboards.

How to Interpret Reputation Scores

A score from a checker is a symptom. Ask why it is what it is: a spike in complaints from a new campaign, a broken authentication record, a stale list.

A weak reputation does not always mean outright blocking. Providers may also slow down delivery (throttling, shown as temporary errors in Postmaster Tools) or send part of your mail to spam.

Reading Reputation Tiers

Each tool grades differently. Postmaster Tools uses High, Medium, Low or Bad in the legacy interface only. The others:

• Microsoft SNDS: green when under 10% of messages get a spam verdict, yellow from 10% to 90%, red above 90%; IPs that sent fewer than 100 messages that day may show no data (Microsoft)

• Sender Score: 0 to 100; Validity says that with a score below 91 "your inbox placement rate on average will be at least 20 percent lower" (2019 benchmark, Validity)

A sudden drop is more urgent than a steady low score: it points to a recent event, such as a new campaign or a bad list import, that you can find and undo.

Reputation Score Diagnostics Checklist

Check the content side too, with a spam test.

What to Do When Reputation Drops

Work through these steps in order:

1. Confirm the drop in a second source. Compare Postmaster Tools delivery errors, the bounce texts in your sending logs and a placement test

2. Stop the campaign that caused it. Pause the segment that went out just before the drop; keep sending from healthy domains

3. Check the complaint rate. Keep it under 0.1%. Above 0.3%, bulk senders to Gmail are ineligible for Google's delivery mitigation; they become "eligible for mitigation when their spam rates remain below 0.3% for 7 consecutive days." See what spam complaint rate is too high

4. Check blocklists. Look up the domain and sending IPs with the blacklist check skill, MXToolbox or the Spamhaus reputation checker, where Spamhaus handles its domain blocklist removals. For a listed domain, Google says: "Contact the organizations that blocklisted the sending domain and ask that it be removed." Fix the cause before you ask

5. Run a placement test with a neutral control email. Send it and your campaign email from the same mailboxes in the same minute. If only the campaign email lands in spam, the copy is the problem; if both do, look at the domain or the sending IPs. See are inbox placement tests reliable

6. Decide whether the domain is burned. The burned domain detector compares each domain with its own history and returns keep, rest or retire; what to do with a burned domain covers each case

7. Try new copy before buying new domains. The FAQ on our pricing page says: "Before you buy new domains, try new copy. In our data, fresh domains sending the same copy from the same servers did no better than the old ones. Rewritten copy did." Step 5 shows whether the copy is the cause

8. Restart low and raise volume in steps. Google: "If messages start bouncing or start being deferred, reduce the sending volume until the SMTP error rate decreases. Then, increase slowly again." (Google)

How to Build a Strong Domain Reputation

A checker spots trouble. Good habits prevent it: build a history of steady, wanted mail before you send at volume.

Warm Up New Domains

A new domain has no reputation, and providers are wary of senders without history. Google's advice: "Start with a low sending volume to engaged users, and slowly increase the volume over time."

For cold email we recommend warm-up only for the first 14 days, cold email from day 14 at a low volume, and up to 25 cold emails per mailbox a day around day 21, with warm-up still running. The day-by-day plan and the checks before each step are in the email warm-up schedule.

Keep Your List Clean

A sunset policy removes contacts who have not opened or clicked in a set period, for example 90 or 180 days. Emailing unengaged people lowers your engagement and raises the risk of hitting recycled spam traps. Verify your list regularly, for example once a quarter and before large sends.

Your Domain Reputation Questions, Answered

How Often Should I Check My Reputation?

At least weekly as routine. Daily while warming up a new domain, after a large campaign, or while recovering from a problem. The point is to catch a drop right after the send that caused it.

Can I Fix a Bad Reputation Overnight?

No. Recovery takes weeks of consistent, clean sending. Pause sends to segments with high bounce or complaint rates, send only to your most engaged contacts for a while, and check that SPF, DKIM and DMARC pass.

Why Are My Scores Different Across Tools?

Each checker uses different data. Sender Score rates sending IPs; Postmaster Tools reports only mail to personal Gmail accounts; SNDS reports only Outlook.com traffic from IPs you control; blocklists each have their own criteria. Use several tools for the full picture.

How Do I Check My Domain Reputation for Free?

Combine the free tools:

• Gmail: Google Postmaster Tools, with Compliance status, Spam rate, Delivery errors and the Deliverability analysis

• Outlook.com: Microsoft SNDS, if you control your sending IPs

• Blocklists: the MXToolbox Blacklist Check or the Spamhaus reputation checker, plus Google's Safe Browsing site status page, which Google asks senders to check regularly

• Authentication: our SPF, DKIM and DMARC checker

• Placement: the GlockApps free plan, with 2 spam tests

Low-volume domains may show no data in Postmaster Tools or SNDS; then the placement test and your own bounce and reply numbers carry more weight.

For seed selection, the control email and repeated tests, follow the inbox placement test guide.

Sources

Checked October 1, 2026:

• Gmail Help: Deprecation of the old Postmaster Tools interface

• Gmail Help: Postmaster Tools dashboards

• Gmail Help: Set up Postmaster Tools

• Google: Email sender guidelines and FAQ

• Microsoft SNDS and SNDS FAQ

• Sender Score and Validity: Sender Score benchmark

• MXToolbox Blacklist Check and MXToolbox plans

• GlockApps and GlockApps pricing

• Validity Engage, where the Everest page now redirects

• Spamhaus Domain Blocklist

Outreach2day sets up the domains, the SPF, DKIM and DMARC records and the warm-up for every mailbox, and each mailbox shows its warm-up inbox, spam and bounce rate, at $2.50 per mailbox a month.