You're sending the same emails to the same list, but your click rates are dropping. Nothing changed on your end, yet more of your messages are landing in spam. The likely cause is your domain reputation.
Every mailbox provider, Gmail, Outlook, Yahoo, and others, maintains its own score for how trustworthy your domain is, each based on its own criteria. That score determines whether your emails reach the inbox, get filtered to spam, or get rejected. You can have a good reputation with Gmail and a mediocre one with Outlook at the same time.
What affects your domain reputation
While each provider uses its own algorithm, the key signals are well known: spam complaints, authentication, bounce rates, engagement, and sending patterns. Our email deliverability guide covers each factor in depth.
How to check your domain reputation
No single tool shows your full domain reputation, but a few free tools together can give you a useful picture:
- Google Postmaster Tools - direct compliance and spam rate data from Gmail
- Spamhaus - domain reputation scoring
- Talos Intelligence - domain and IP reputation lookup
- Sender Score - IP reputation aggregated across 80+ mailbox providers
- MXToolbox - blocklist checking across 100+ lists
Google Postmaster Tools
Google Postmaster Tools shows you how Gmail views your domain. If you send any meaningful volume to Gmail addresses, start here.
Focus on two dashboards. Compliance Status shows a pass/fail for Gmail's sender requirements: authentication, one-click unsubscribe, and spam rate. Spam Rate shows the percentage of your emails that recipients marked as spam, with threshold lines at 0.10% and 0.30%. Cross 0.30% and Gmail starts rejecting your emails.
To get started, add and verify your sending domain. You'll need DKIM authentication and at least 250 daily messages to Gmail users before data populates.
Sendfully walks you through setting up DKIM, SPF, and DMARC step by step, and shows you whether each one is verified. You'll know authentication is working before you check Postmaster Tools.
Spamhaus
Spamhaus is a nonprofit that maintains some of the most widely used blocklists in email. Their domain reputation page scores your domain based on signals observed across their network.
Many mailbox providers and corporate mail servers use Spamhaus data directly in their filtering decisions, so a poor score here often shows up as deliverability problems elsewhere.
Talos Intelligence
Talos Intelligence is Cisco's reputation lookup tool. Enter your domain or IP and you'll get a rating of "Good", "Neutral", or "Poor".
Don't worry if you see "Neutral". It's the most common result and usually just means Talos doesn't have enough data to rate you higher. "Good" means consistent, clean sending over time. "Poor" means Talos has flagged a problem and your emails are likely being filtered or blocked.
Sender Score
Sender Score rates your sending IP address on a 0 to 100 scale, drawing data from more than 80 mailbox and security providers worldwide.
The score factors in spam complaints, blocklist presence, and infrastructure. Below 70 means your IP has been flagged for risky sending behavior. 70 to 80 is acceptable with room to improve. Above 80 reflects a healthy sending history.
One thing to keep in mind: Sender Score measures IP reputation, not domain reputation. The score reflects all senders sharing that IP, so if you're on shared sending infrastructure, a poor score may not be entirely within your control.
Sender Score requires your name, company, and email address before showing results.
MXToolbox
MXToolbox is a free blocklist checker that scans your domain or IP against over 100 blocklists at once, including Spamhaus, Barracuda, and many others.
You get a simple pass/fail for each list. If you show up on a major list like Spamhaus or Barracuda, that's worth investigating. Many mailbox providers use these lists directly in their delivery decisions.
Quick comparison
A quick comparison of all five:
| Tool | What it measures | Rating system |
|---|---|---|
| Google Postmaster Tools | Gmail compliance and spam rate | Pass/Fail + percentage |
| Spamhaus | Domain reputation | Reputation score |
| Talos Intelligence | Domain and IP reputation | Good/Neutral/Poor |
| Sender Score | IP reputation across 80+ providers | 0-100 score |
| MXToolbox | Blocklist presence across 100+ lists | Listed/Not listed |
What to do with your results
You'll likely get different results from different tools. That's expected, since each one measures different things from different data sources. Here's how to read your results and what to do about them.
Compliance failures
A compliance failure in Postmaster Tools is the most urgent thing to fix. Since November 2025, Gmail rejects non-compliant email rather than filtering it to spam. Your emails aren't being delivered at all.
Check that SPF, DKIM, and DMARC are properly configured for your domain, and that your emails include a working one-click unsubscribe header. Our email deliverability guide walks through each step.
Sendfully monitors your DNS records and alerts you if your DKIM, SPF, or DMARC configuration breaks, so you'll catch compliance problems before they affect your reputation.
High spam rate
Spam rate is the other number to watch closely. Between 0.1% and 0.3% puts you in warning territory. Above 0.3% and Gmail starts rejecting your email.
If your spam rate is elevated, our guide to avoiding the spam folder and list hygiene steps cover what to fix and in what order.
Low reputation scores
A low score in Spamhaus, a "Poor" rating in Talos, or a Sender Score below 70 all suggest mailbox providers may throttle or block your messages.
The recovery process is the same regardless of which tool flagged the problem. Fix your authentication first, remove contacts who have bounced or filed a spam complaint, and pause non-essential campaigns. When you resume, send in smaller batches and increase volume gradually as your scores improve. Recovery typically takes 30 to 60 days, though domains on major blocklists may need longer.
Blocklist appearances
If MXToolbox shows you listed on a blocklist like Spamhaus, don't ignore it. Most blocklists have a removal request process, but they'll want you to fix the underlying problem first, so start there.
Little or no data
If you're seeing little or no data, that usually means your domain has no reputation yet, not a bad one. That's a fine place to start. Our email deliverability guide covers what to do from here.
Build a monitoring routine
A spam rate that climbs from 0.05% to 0.07% is easy to correct. A spam rate that hits 0.4% before you notice could take months to recover from. The tools are free and the checks take minutes. Make them part of your routine.
- Review bounces, complaints, and unsubscribes in your email platform
- Check your compliance status and spam rate
- Run a blocklist check and review your reputation scores
- Clean your list by removing contacts who haven't engaged recently
Most reputation problems are fixable, and the earlier you spot them, the easier they are to turn around.