There is no single number you can look up. To check sender reputation, you go to the mailbox providers themselves, and the two biggest run free dashboards for exactly this. Google Postmaster Tools shows how Gmail rates your domain and your IP address (the numeric address of the server that sends your mail). Microsoft’s Smart Network Data Services, SNDS for short, shows how Outlook and Hotmail treat your IP. Add a blacklist lookup, your own bounce and complaint reports and a test send to inboxes you own, and you have as complete a picture as anyone outside those companies can get.
Sender reputation, for anyone new to the term, is the running score a mailbox provider keeps on your domain and IP, built from bounces, spam complaints and how recipients treat your mail. We covered the causes in why emails go to spam even when the content is fine. This post is about the checking: where to look, what the screens mean, and what to do next.
Where to check sender reputation, provider by provider
1. Google Postmaster Tools (Gmail)
If you check one thing, check this. Gmail holds a large share of most consumer lists, and Google Postmaster Tools is free and takes about ten minutes to set up.
Once your domain is verified you get these dashboards:
- Compliance status. Whether your domain meets Google’s sender requirements, item by item.
- Spam rate. The share of your messages that Gmail users reported as spam, per day.
- Domain reputation. Gmail’s rating of your sending domain, in four bands: Bad, Low, Medium and High.
- IP reputation. The same for the IP addresses that deliver your mail. Matters mostly on a dedicated IP.
- Authentication. How much of your traffic passed SPF, DKIM and DMARC, the three DNS records (public settings on your domain name) that prove a message really comes from your domain.
- Encryption. Share of mail delivered over an encrypted (TLS) connection; usually near 100%.
- Delivery errors. Messages Gmail rejected or deferred, with the reason.
- Feedback loop. Complaint data for senders who tag campaigns with a special header. Most small senders can skip it.
The bands are the part everyone wants, and Google’s dashboard help defines them. High: “History of very low spam rates, and complies with Gmail’s sender guidelines”, with mail “rarely marked as spam by Gmail”. Medium: legitimate email with occasional spam, and “a fair deliverability rate, except when there’s a notable increase in spam”. Low: “History of sending a significant volume of spam regularly”, with mail “likely to be marked as spam”. Bad: a high volume of spam regularly, and mail “almost always marked as spam or rejected by the receiving server”. The band is a summary, though. The spam rate chart underneath is what moves it.
Adding a domain. Sign in with a Google account, choose “Add new domain” and enter your domain. Google asks for the domain in your SPF Return-Path (the hidden address bounces go back to) or your DKIM signature. For many senders that is the From domain, but if your tool signs mail with its own domain, that is the one Gmail is scoring. Copy the TXT or CNAME record Google gives you into your domain’s DNS settings and click Verify. Google’s help page says: “Typically, Postmaster Tools verifies domains right away, but it can take up to 10 minutes.”
“Not enough data”. Small senders often verify a domain and see nothing. Google’s help page explains why: “Data might be missing if the total number of messages for a given day is too low. This is to protect users’ privacy.” The threshold is not published. In my experience a few hundred messages a day to Gmail gets you some days and not others. That is not a bad sign. You are too small to measure, so the other checks below matter more for you.
2. Microsoft SNDS (Outlook, Hotmail, Live)
Smart Network Data Services is Microsoft’s equivalent, with one important difference: it reports on IP addresses rather than domains.
You log in with a Microsoft account, request access to the IPs you send from, and complete Microsoft’s authorization step, which confirms you are responsible for them. Then, for each day you sent enough mail, you see the volume Microsoft received, a color-coded filter result (green, yellow or red, depending on how much of it its filters judged to be spam), and the complaint rate from Outlook.com users. SNDS used to report spam-trap hits as well; Microsoft’s page says trap hit counts are no longer included in the data report as of July 2026. Alongside it sits the Junk Email Reporting Program, which sends you a report when an Outlook.com user marks your message as junk. It is free.
On a shared IP, where your email service delivers mail for many customers from the same address, SNDS shows your provider’s IP and everyone else on it, and you may not be able to authorize it at all. The good providers watch it for you. On a dedicated IP, SNDS is essential and worth a weekly look.
3. Yahoo and AOL
Yahoo does not offer a reputation dashboard. It has a Sender Hub with published best practices, and a complaint feedback loop you can apply for, which notifies you when a Yahoo or AOL user marks your mail as spam. As far as I know, enrolment is keyed to your DKIM domain, so DKIM has to work first. Beyond that, your view into Yahoo is indirect: bounce messages and the test send below.
4. Blacklist lookups
Blacklists are public lists of IP addresses and domains that mail servers consult before accepting a message. They are not reputation scores, but a listing means something has already crossed a line, and free sites check dozens of lists in one query. Our guide to checking whether your domain is blacklisted covers the lookups and what to do about a listing.
5. Your own sending tool, plus a seed test
Your email platform’s own reports are the check most people skip, and the only one that covers every provider at once. After each campaign, look at the hard bounce rate (messages to addresses that do not exist) and the complaint rate, and watch the trend across the last five or six sends. Our post on what counts as a good email bounce rate gives the ranges.
A seed test is the rough placement check: create a few free mailboxes at Gmail, Outlook and Yahoo, add them to your list, and see where each send lands. It is crude, since your test addresses have no engagement history and real subscribers may be treated differently. But if all three seeds go to spam on the same day, you have learned something in five minutes.
The tools at a glance
| Tool | What it shows | Who it covers | Cost |
|---|---|---|---|
| Google Postmaster Tools | Domain and IP reputation bands, spam rate, authentication, encryption, delivery errors | Gmail and Google Workspace | Free |
| Microsoft SNDS | Per-IP volume, color-coded filter result, complaint rate; junk-report feedback | Outlook.com, Hotmail, Live | Free |
| Yahoo Sender Hub and feedback loop | Best practices; notification of complaints | Yahoo and AOL | Free |
| Blacklist lookup sites | Whether your IP or domain appears on public blocklists | Any server that consults them | Free for lookups |
| Your sending tool’s reports | Bounce and complaint rates per campaign | Every provider you send to | Included with the tool |
| Seed-inbox test | Rough inbox-or-spam placement | Whichever mailboxes you create | Free, your time |
How to read the numbers
Read trends, not snapshots. A single bad day is noise. Three weeks of a spam rate drifting from 0.05% to 0.2% is a trend, and it will reach your reputation band a few weeks later.
Match the dates to your campaigns. Every dip has a send behind it. Put your campaign calendar next to the chart and the culprit is usually obvious, like the re-engagement blast to a two-year-old segment.
Google’s sender guidelines give you a scale: “Keep spam rates reported in Postmaster Tools below 0.3%”, and for senders of more than 5,000 messages a day, “Keep spam rates reported in Postmaster Tools below 0.10% and avoid ever reaching a spam rate of 0.30% or higher.” So 0.1% is the comfortable zone, 0.3% is the line you never want to touch, and anything in between means a segment of your list no longer wants your mail.
A common picture: domain reputation Medium, spam rate creeping upward, authentication at 100%. That says the setup is fine and the list is the problem. Gmail still delivers most of your mail, but a growing group of recipients is reporting it, and if the rate stays above 0.3% the band drops to Low and much of your mail starts going to spam. Medium is a warning you can still act on. Low is a recovery project.
How to improve your sender reputation
In order of impact, from what I have seen fixing these.
- Fix authentication and alignment. Confirm SPF, DKIM and DMARC all pass on a test message, and that the domain passing them is your visible From domain (that match is called alignment). Nothing else on this list helps much while this is broken.
- Cut the dead addresses and spam traps. Hard bounces and trap hits damage reputation fastest, and both come from the list, not the content. Running your list through Reoon Email Verifier before a send removes the addresses that no longer exist and flags known spam traps (addresses that exist only to catch careless senders) and disposable addresses, at an advertised 99%+ accuracy. It does not repair a reputation by itself, but it helps by removing the bounces that keep dragging the score down. A free account includes free verification credits every day, no card required.
- Stop mailing the unengaged. Anyone who has not opened or clicked in six to twelve months adds complaint risk and no benefit. Send one honest “still want these?” message, then remove the silent ones.
- Keep volume steady. Providers trust patterns. Send similar amounts on a similar rhythm, and ramp new domains or IPs over several weeks. Google’s guidelines say that as you increase volume you should monitor delivery in Postmaster Tools.
- Make unsubscribing easy. A one-click unsubscribe in the header and a visible link in the footer turn would-be complaints into harmless list exits. Our guide to how one-click unsubscribe works covers the setup.
- Wait. Reputation is a rolling average of recent weeks, so nothing you do today shows up tomorrow. Expect two to four weeks of steady, clean sending before the band moves, longer from Low or Bad.
My honest opinion
Most small senders never open Postmaster Tools, and honestly, below a few hundred Gmail messages a day it would show them little anyway. The ones who do are nearly always there because something already went wrong, and what they find is usually a spam rate chart that mirrors their bounce report: a list problem wearing a reputation costume. The dashboards confirm that well. They are weaker at telling you which addresses caused it, which is why the bounce report and a verification pass do the real diagnostic work.
If you have never verified your list, do that before you spend an afternoon reading charts. You can open a free Reoon account, run a sample, and know within minutes whether the addresses are the reason the needle will not move.
FAQ
Is there one place to check sender reputation for all providers?
No. Each provider keeps its own reputation data, and only Google and Microsoft publish sender-facing dashboards. Postmaster Tools covers Gmail by domain and IP, SNDS covers Outlook and Hotmail by IP, and for everyone else you rely on blacklist lookups, your own bounce and complaint reports, and test sends to mailboxes you control.
Why does Google Postmaster Tools show no data for my domain?
Almost always because your daily volume to Gmail is too small. Google says data may be missing when the number of messages on a given day is too low, to protect user privacy, and it does not publish the threshold. Check that the verified domain matches your DKIM or Return-Path domain, then look again as volume grows. Empty charts do not mean a bad reputation.
Does sender reputation belong to my domain or my IP address?
Both, tracked separately. Domain reputation follows you wherever you send from and is the one you fully control. IP reputation attaches to the server address, which on a shared IP is shaped by every other customer using it. That is why switching email providers rarely rescues a damaged domain, and why a poor IP score with a good domain score usually points at your provider.
How often should I check my sender reputation?
Monthly is enough when volume and results are steady. Move to weekly for a month after any change: a new sending tool, a new domain, a large list import or a jump in volume. Check daily only while recovering from a problem, and remember that the charts lag by a day or two and reputation bands move in weeks.
