Your email sender reputation is a score maintained by inbox providers that determines whether your emails land in the inbox, promotions tab, or spam folder. It is calculated from your bounce rate, spam complaint rate, engagement history, and authentication compliance. A high reputation (Sender Score 80+, Google Postmaster "High") means reliable inbox placement. A damaged reputation requires weeks of disciplined, low-volume sending to rebuild. You can check your reputation for free using Google Postmaster Tools, Sender Score, MXToolbox, and Mail-Tester.
What Email Sender Reputation Is
Email sender reputation is not a single number from a single source. It's a composite assessment made independently by each major inbox provider (Google, Microsoft, Yahoo) based on their own signals from their own users.
The core signals that build or damage your reputation:
Related guide: cold email deliverability tool
| Signal | Good for Reputation | Bad for Reputation |
|---|---|---|
| Bounce rate | Under 1% | Above 3% |
| Spam complaint rate | Under 0.05% | Above 0.10% |
| Open/reply rate | High engagement | Near-zero engagement |
| Authentication | SPF + DKIM + DMARC all passing | Any failing |
| Volume consistency | Steady, gradual growth | Sudden spikes |
| List freshness | Verified, current contacts | Old, unverified lists |
| Prior history | Long clean track record | New domain or past incidents |
Inbox providers evaluate these signals cumulatively. A single bad campaign won't destroy years of good reputation, but sustained problems compound quickly.
Domain vs. IP Reputation
Domain reputation is attached to your sending domain (yourdomain.com). It's the primary reputation signal for modern email delivery. Google Postmaster Tools reports domain reputation specifically.
IP reputation is attached to the IP address your emails are sent from. If you use a shared ESP, your IP reputation is shared with all other senders on that IP — a problem if any of them send spam. If you use a dedicated IP, you build and own your IP reputation.
Related guide: cold email deliverability tool
For most cold email senders using reputable ESPs, domain reputation is the higher-leverage signal to monitor and protect. IP reputation matters primarily for very high-volume senders or teams on lower-quality shared infrastructure.
How to Check Your Sender Reputation
Tool 1: Google Postmaster Tools (Most Important)
URL: postmaster.google.com
Postmaster Tools is free and gives you direct insight into how Gmail — the most important inbox provider for B2B — sees your domain.
Related guide: how to improve best email outreach tool
Setup:
- Go to postmaster.google.com
- Click "Add a domain"
- Enter your sending domain
- Verify ownership by adding a TXT record to DNS (Google provides the specific record)
- Allow 24–48 hours for data to populate
What to monitor:
- Domain Reputation — Rated as High, Medium, Low, or Bad
- High: Strong inbox placement expected
- Medium: Adequate but worth improving
- Low: Deliverability significantly impacted
- Bad: Emails likely going to spam for most Gmail recipients
- Spam Rate — Percentage of emails your Gmail recipients mark as spam
- Target: Below 0.05%
- Warning: Above 0.10%
- Critical: Above 0.30% (Google will begin filtering aggressively)
- Authentication — Pass rates for SPF, DKIM, and DMARC
- Target: 100% pass rate on all three
Check frequency: Weekly during active campaigns; monthly during low-volume periods.
Related guide: email outreach platform guide by SalesOutreach
Tool 2: Sender Score (senderscore.org)
URL: senderscore.org
Sender Score provides a 0–100 score for your sending IP address, updated daily. It's maintained by Validity (formerly Return Path) and used as a reference signal by many inbox providers.
Score interpretation:
- 80–100: Strong reputation; good inbox placement expected
- 70–79: Moderate; monitor actively for further decline
- Below 70: Damaged reputation; deliverability likely impacted; action required
How to use: Enter your sending IP address. If you're on a shared ESP, the IP shown in your sent email headers is what to check. Use a tool like MXToolbox's Email Header Analyzer to extract the sending IP from a sent email's headers.
Limitation: Sender Score reflects IP reputation, not domain reputation. It's one signal in a broader picture — use alongside Postmaster Tools for a complete view.
Tool 3: MXToolbox Blacklist Check
URL: mxtoolbox.com/blacklists.aspx
MXToolbox checks your sending domain and IP against 100+ major spam blacklists simultaneously. Blacklisting is the most severe form of reputation damage — being listed on Spamhaus, Barracuda, or SpamCop causes significant delivery failure at most inbox providers.
How to use:
- Enter your sending domain or IP
- MXToolbox checks all major blacklists in seconds
- Any listing appears in red with the blacklist name and reason
If you're listed: Each blacklist has its own removal process. Most require:
- Identifying and fixing the root cause (high bounce rate, spam complaints, sending to spam traps)
- Submitting a delisting request with evidence that the issue is resolved
- Waiting 1–7 days for removal to process
Run a blacklist check after any campaign that produces higher-than-normal bounces or complaints, and monthly as a routine check.
Tool 4: Mail-Tester (mail-tester.com)
Mail-Tester gives you a comprehensive 1–10 deliverability score by simulating what a receiving server sees when it evaluates your email. It checks authentication, content, spam indicators, and list hygiene signals.
How to use:
- Go to mail-tester.com — it provides a unique test email address
- Send a real campaign email to that address (using your actual sending domain and platform)
- Return to Mail-Tester within a few minutes to see your score and itemized breakdown
What it checks:
- SPF, DKIM, DMARC authentication
- Spam trigger word detection in subject and body
- Link analysis (number of links, domain reputation of linked URLs)
- HTML vs. plain text formatting
- Sending IP reputation
Target score: 8/10 or above before launching any campaign. Below 7/10 means something is wrong that needs fixing first.
Signs Your Reputation Has Been Damaged
Watch for these warning signals in your campaign data:
Leading indicators (catch these early):
- Open rate dropping 30%+ from your recent baseline
- Bounce rate climbing above 2%
- More "out of office" replies than usual (can indicate deliverability issues, not actual engagement)
Lagging indicators (problems already developing):
- Spam complaint rate above 0.10% in Postmaster Tools
- Postmaster domain reputation drops to "Medium" or "Low"
- Sender Score drops below 70
- MXToolbox shows a blacklist listing
Score thresholds requiring immediate action:
- Sender Score below 60
- Postmaster domain reputation: "Bad"
- Spam rate above 0.30%
- Bounce rate above 5%
- Any Spamhaus blacklist listing
How to Fix a Damaged Sender Reputation
Recovery requires patience. There is no quick fix — inbox providers update reputation signals based on actual sending behavior over time. The protocol:
Week 1: Stop the bleeding
- Pause all high-volume sending immediately
- Run your full list through real-time email verification — remove all invalid addresses, bounces, and unsubscribes
- Check and fix authentication (SPF, DKIM, DMARC) if any are failing
- Submit blacklist removal requests if you're listed (after fixing the root cause)
Weeks 1–2: Rebuild list hygiene
- Remove role-based addresses (info@, admin@, support@)
- Remove contacts from previous complaint sources if identifiable
- Segment your remaining list to identify the highest-quality, most-engaged contacts
Weeks 2–4: Resume at low volume with best contacts
- Resume sending at 20% of your previous maximum volume
- Send only to your most engaged, highest-fit contacts — the people most likely to open, reply, and not complain
- Keep content clean, relevant, and personalized
- Monitor Postmaster Tools and Sender Score weekly
Weeks 4–8: Gradual ramp
- Increase volume by 20–30% per week as reputation metrics stabilize
- Target Postmaster domain reputation "Medium" before scaling past 50% of previous volume
- Target "High" before returning to full campaign volume
Full recovery timeline: 4–8 weeks for moderate damage; 8–12 weeks for severe damage including blacklisting. Rushing the ramp resets the recovery clock.
Prevention Is Far Easier Than Recovery
The most efficient deliverability strategy is not repairing damage — it's preventing it.
Weekly habits that prevent reputation damage:
- Check Postmaster Tools every Monday — 5 minutes, catches problems before they compound
- Verify every new list before first send
- Monitor bounce rate per campaign — remove all hard bounces immediately
- Review spam complaint rate after each campaign blast
System-level practices:
- Run a warm-up tool continuously, not just during initial ramp
- Use a dedicated sending domain so primary domain is never at risk
- Maintain a suppression list (all-time unsubscribes + complaints) applied to every campaign
- Set a hard bounce rate alert at 2% — if it triggers, pause and investigate before continuing
Frequently Asked Questions
Q: What is a good email sender reputation score?
On Sender Score, a score of 80 or above indicates a healthy sender reputation with good inbox placement rates. Scores between 70–79 warrant monitoring and active list hygiene. Scores below 70 indicate a damaged reputation likely causing significant spam folder placement. Google Postmaster Tools rates domain reputation as High, Medium, Low, or Bad — "High" is the target for cold email senders.
Q: How long does it take to recover from a bad sender reputation?
Recovering a damaged sender reputation typically takes 4–12 weeks depending on severity. The process involves pausing or drastically reducing send volume, removing bad addresses, sending only to your most engaged contacts, and gradually increasing volume again as reputation metrics improve. Blacklist removal (via Spamhaus or Barracuda) can take 1–4 weeks after the underlying issue is resolved.
Q: What causes a bad email sender reputation?
The main causes are high bounce rates (above 2–3%), high spam complaint rates (above 0.1% for Gmail), sending to purchased or old unverified lists, not having SPF/DKIM/DMARC configured, and sending high volumes without warming up the domain first. A sudden spike in send volume from a previously low-volume domain also triggers reputation flags.
Q: How often should I check my sender reputation?
Weekly during active campaigns. The minimum: Google Postmaster Tools domain reputation and spam rate weekly; MXToolbox blacklist check monthly and after any high-bounce campaign; Sender Score monthly as a baseline check. Mail-Tester before every new campaign launch.
Q: Can I improve sender reputation without stopping campaigns?
Yes, for moderate reputation issues. The keys: verify and clean your list immediately, reduce send volume by 30–50%, improve targeting to increase reply rate (engagement signals help reputation recovery), and ensure authentication is 100% passing. For severely damaged reputation (Postmaster "Bad", Sender Score below 60), pausing high-volume sending is usually necessary.