Sender reputation is the running score every mailbox provider keeps on you, and it's the invisible variable behind most "why is my mail going to spam?" mysteries. Two senders can pass the same authentication checks and send the same content, yet one lands in the inbox and the other in spam — because the provider trusts one more than the other. This is what that trust is made of, and how to protect it.
The short answer#
Reputation is built from your sending history: spam complaints, hard bounces, spam-trap hits, how people engage with your mail, and how consistently you send. Providers track it for both your sending IP and your domain, and they act on it every time you send. It is slow to build and fast to lose, which is why the work is preventive — you protect a good reputation continuously, because repairing a damaged one takes weeks.
There is no single score you can look up. Gmail, Microsoft, and every other provider keep their own view of you, so you check it provider by provider.
IP reputation vs domain reputation#
There are two scores, and the difference matters:
- IP reputation attaches to the server your mail is sent from. On a shared IP (most ESPs), you inherit the pooled reputation of everyone else on it; on a dedicated IP, the reputation is entirely yours to build — and to warm up.
- Domain reputation attaches to your sending domain and travels with your brand. It's the one you can't escape by switching servers — and over time it matters more than IP reputation, because it's tied to you, not to infrastructure.
A sending subdomain such as
news.example.com builds its own history, largely separate from your root
domain, so a noisy marketing stream is less likely to drag down your receipts and
password resets. It only isolates reputation if the visible From address uses
the subdomain, and it's insulation, not a firewall. Whether you also need your
own IP is a separate call: see shared or dedicated IP.
Switching IPs to dodge a bad reputation doesn't work if your domain reputation is the problem. Fix the cause, don't move the address.
What moves your reputation#
Providers weigh a handful of signals. None of them publishes the exact weights, but these are the ones that move it:
- Spam complaints. The single loudest negative signal — someone hitting "report spam". Gmail and Yahoo require a spam complaint rate under 0.3%, and that is a ceiling, not a target: aim below 0.1%. Feedback loops at most providers (Gmail is the exception) tell you who complained, so you can suppress them.
- Hard bounces. Mailing dead addresses signals you don't maintain your list. Sustained bounces drag reputation down fast.
- Spam-trap hits. Hitting a spam trap is strong evidence of poor list hygiene and can get you blocklisted.
- Blocklist listings. A listing on a major blocklist such as Spamhaus is a negative signal in its own right, and the harm can outlast the listing. Here is how a blacklist listing damages your reputation.
- Engagement. Opens, clicks, and replies build reputation; being ignored, deleted unread, or filed as spam erodes it. When you measure engagement yourself, lean on clicks, replies, and purchases: Apple Mail Privacy Protection pre-loads images, so your open rate overstates how many people actually read you. Engaged recipients are the best reputation asset you have.
- Volume and consistency. Steady, predictable sending reads as legitimate; a sudden spike from a quiet domain reads as a compromised account or a spammer. The classic spikes are emailing an old list nobody has touched in months, and jumping from weekly sends to daily ones in the Black Friday rush.
- Authentication. SPF, DKIM, and DMARC are the prerequisite — without them, there's no identity to attach a reputation to in the first place. Since February 2024 the Gmail and Yahoo sender requirements make them mandatory for bulk senders (roughly 5,000+ messages a day to Gmail), and Microsoft began enforcing the same for Outlook.com in May 2025.
How to check your sender reputation#
No one tool shows the whole picture. Read these sources together, and look for a slip at a single provider rather than an average across all of them:
| Source | What to look at | What a slip looks like |
|---|---|---|
| Google Postmaster Tools | Spam rate, compliance status (authentication, one-click unsubscribe) and delivery errors for mail to Gmail. | Spam rate climbing above 0.1% (don't wait for 0.3%), a requirement falling out of compliance, or more rejected and deferred mail. |
| Microsoft SNDS | A green, yellow, or red filter result per IP for Outlook.com, Hotmail, and Live. Only covers IPs you control. | An IP turning yellow or red. |
| Blocklist lookup | Look up your sending IP with the free blacklist checker, or watch your domains and IPs with blacklist monitoring, which re-checks them every 24 hours. | A new listing. |
| Your bounce and deferral codes | Your sending platform's bounce log, broken down by receiving provider. | 4.7.x throttling or 5.7.x policy blocks concentrated at one provider. |
| Inbox placement test | Where a test send lands (inbox, spam, or missing) at each provider. Seed accounts aren't your subscribers, so treat it as directional. | Placement dropping at one provider while the others hold. |
Third-party reputation scores are estimates built from each vendor's own data. They can point at a problem, but Gmail and Microsoft decide placement on their own signals, so trust the provider tools first.
How to protect a good reputation#
None of this is exotic; it's discipline applied consistently:
- Verify your list so hard bounces and spam-trap hits — the two fastest ways to lose reputation — mostly don't happen. Removing dead addresses before you send is the highest-leverage preventive step. To test a single address, use the free email checker.
- Collect with permission and make unsubscribing easy, so complaints stay low. Never mail bought or rented lists: nobody on them asked to hear from you.
- Send consistently to engaged people, and sunset the ones who've gone quiet with a sunset policy.
- Warm up any new domain or IP rather than starting at full volume. Treat a move to a new platform the same way; the guide to switching email providers covers what carries over.
- Check the sources above monthly and after any unusual send, instead of waiting for placement to drop. A monthly list health check turns that into a routine with clear thresholds.
How to repair a damaged reputation#
There's no reset button, and anyone selling one is selling snake oil. Recovery is slow and deliberate:
- Find where and why. Use the sources above to pin down which provider is unhappy, then find the segment, campaign, or signup source behind the complaints or bounces. A 5.7.x block at one provider points to reputation, content, a blocklist, or authentication rather than bad addresses; 4.7.x deferrals across that provider, send after send, mean you're being throttled. If a blocklist is involved, fixing its cause and getting delisted come before anything else, and recovery takes longer because the damage outlasts the listing.
- Fix the cause. Clean the list, repair authentication, and stop whatever generated the complaints or bounces — otherwise you're pouring water into a leaking bucket.
- Slow down and re-warm. Cut volume sharply and send only to your most engaged subscribers — the people most likely to open and least likely to complain — then rebuild volume gradually.
- Be patient and watch the tools. Reputation is earned back over weeks of consistent good sending. Watch your spam rate, compliance status, and bounce and deferral trends to confirm it's recovering before you scale back up.
Frequently asked questions
01What is a good sender reputation?
One where providers consistently put your mail in the inbox. In practice that means a spam complaint rate under 0.1% and never near 0.3%, hard bounces near zero, a passing compliance status in Google Postmaster Tools, a green SNDS result on any IPs you control, and no listings on major blocklists. There's no single universal number to hit, and the current Postmaster Tools doesn't grade reputation as High, Medium, Low, or Bad, so read those signals together.
02How do I check my sender reputation?
Check it provider by provider. In Google Postmaster Tools, watch your spam rate, compliance status, and delivery errors; the current version no longer shows the old domain and IP reputation grades. Microsoft SNDS shows a green, yellow, or red result for Outlook.com, but only for IPs you control. Add a blocklist check and your own bounce and deferral codes broken down by provider. Third-party services estimate a reputation score, but the provider tools show you what actually decides placement to their users.
03How long does it take to repair a damaged sender reputation?
Weeks, not days - and only after you've fixed the underlying cause. Reputation is built from a rolling history of your sending, so it recovers as that history fills with good behavior: low complaints, low bounces, and real engagement. Slowing down and mailing only your most engaged subscribers speeds it up; there is no instant fix.
04Is IP or domain reputation more important?
Both matter, but domain reputation matters more over time because it's tied to your brand and travels with you regardless of which server or ESP you use. IP reputation matters most on a dedicated IP you're warming up, or on a shared IP where a bad neighbor can affect you - but you can't outrun a poor domain reputation by changing IPs.
05Does switching email providers reset my sender reputation?
No. Your domain reputation comes with you as long as you keep sending from the same domain and authenticate the new platform with it (your own DKIM signing domain), so a damaged one follows you to the new platform. Only the IP reputation changes: on a shared IP you inherit the new provider's pool, and a new dedicated IP starts with no history and needs warming up. Switching email providers covers what moves with you and what stays behind.
The two fastest ways to lose reputation — hard bounces and spam-trap hits — are also the most preventable. The free plan runs the full verification pipeline so you can strip the dead addresses out before they cost you, and the deliverability guide covers the rest of the levers that keep providers trusting your mail.
