IP reputation is the trust mailbox providers attach to the server address that sends your mail; domain reputation is the trust attached to the domain your mail is authenticated as and sent from. For most senders today, domain reputation matters more, because it follows you across ESPs and IP addresses, and authentication standards like DKIM and DMARC give providers a reliable domain to track. IP reputation still matters, especially for blocklists and for senders with dedicated IPs, but it’s no longer the whole story.

Here’s how each one works, how they interact, and what to do when one of them is the problem.

What is IP reputation?

IP reputation is the history of a specific sending IP address: how much mail it sends, how consistently, and how recipients and spam filters have reacted to that mail.

On a shared IP, your IP reputation is pooled with every other customer using it. Your ESP manages it.
On a dedicated IP, it’s yours alone, and it reflects only your sending.

IP reputation was the main signal in the early days of spam filtering, because IP addresses were the one thing a sender couldn’t fake in an SMTP connection. It’s still used heavily:

Many receiving servers check IP blocklists like Spamhaus SBL and CSS before accepting a connection.
Providers throttle or defer connections from IPs with no history or a sudden surge in volume.
An IP needs regular volume to have a reputation at all. Amazon SES notes that most ISPs only track an IP’s reputation if they receive significant volume from it, and recommends sending several hundred emails within a 24-hour period at least once a month to each ISP where you want to keep a reputation.

What is domain reputation?

Domain reputation is the history attached to the domains in your messages. The most important ones are:

The DKIM signing domain (the d= value in the DKIM-Signature header)
The visible From: domain (what DMARC protects)
The Return-Path / envelope sender domain (what SPF checks)
Link and tracking domains in the body

The M3AAWG Sender Best Common Practices (version 4.0, August 2026) list all of these, plus the HELO name, reverse DNS name, and Reply-To, as domains mailbox providers may use to judge reputation. It recommends using one consistent organizational domain or subdomain across them.

Domain reputation became more important as authentication spread. Once a message is DKIM-signed, a provider can tie it to your domain with confidence, no matter which IP sent it.

Domain reputation vs IP reputation: side-by-side

	IP reputation	Domain reputation
Attached to	The sending server’s IP address	Your DKIM, From:, Return-Path, and link domains
Moves with you when you change ESPs	No	Yes
Shared with other senders	Yes, on shared IPs	Only if you send from a shared ESP domain
Needs steady volume to exist	Yes	Less so, but history still matters
Main blocklists	Spamhaus SBL, CSS, XBL; many others	Spamhaus DBL; URI lists for link domains
Fixed by	Changing sending practices; new IPs need warm-up	Changing sending practices; can’t easily escape
Typical owner	ESP (shared) or you (dedicated)	You

Which one do mailbox providers care about more?

They care about both, and they don’t publish weights. But the trend is clear:

Google’s sender requirements are domain-centric. Since February 1, 2024, Gmail requires SPF or DKIM from all senders, and for bulk senders it requires DMARC and that the From: domain aligns with the SPF or DKIM domain. Google’s Postmaster Tools help says its domain-level data covers messages from the exact domain used for DKIM or SPF authentication.
Yahoo and Microsoft have similar authentication and alignment requirements for bulk senders, per Yahoo’s sender requirements and Microsoft’s Outlook.com postmaster policies.
IPv6 pushes the same way. With so many available addresses, tracking reputation by individual IP gets harder. M3AAWG notes that greater care should be taken with domain reputation when sending over IPv6.

The practical takeaway: a clean IP won’t save a domain that recipients keep reporting, and moving to a new IP won’t wash a bad domain. A good domain reputation, on the other hand, can carry you through moving from one ESP’s shared pool to another.

How the two interact

Think of them as two locks on the same door.

Good domain, bad IP: Common on low-quality shared pools. Your mail may be delayed, deferred, or rejected by servers that check IP blocklists, even though your own history is fine. Fix: talk to your ESP or move to a better pool or a dedicated IP.
Bad domain, good IP: Common when a sender moves to a “clean” new IP to escape problems. The IP has no history, the domain has bad history, and mail goes to spam anyway. Fix: the sending practices, not the infrastructure.
Both bad: Usually a list problem (purchased or very old data) on a dedicated IP. Fix the list, then rebuild slowly.
Both good: Keep doing what you’re doing, and watch for drift.

How to check IP reputation

Find your sending IP. Look at the Received: headers of a message you sent, or ask your ESP.
Check blocklists. Use Spamhaus’s IP and domain reputation checker and a multi-list lookup tool. You can also query a DNSBL directly. For IP 203.0.113.25, reverse the octets and append the list zone:

dig +short 25.113.0.203.zen.spamhaus.org

An answer in 127.0.0.x means listed; no answer means not listed. One catch: Spamhaus refuses queries sent through public or open DNS resolvers and answers with an error code like 127.255.255.254 instead. That’s an error, not a listing, so use their web checker for one-off lookups.

Check Microsoft SNDS if you control the IP. It shows data for your IPs sending to Outlook.com.
Read your SMTP logs. Deferrals and blocks that name your IP tell you more than any score.

How to check domain reputation

Google Postmaster Tools. Verify your domain to see spam rate and compliance status for your mail to Gmail. Google has changed how reputation is shown in the newer version of the tool, so read our post on Postmaster Tools v2 and the retired reputation scores before relying on old dashboards.
Spamhaus DBL. The Domain Blocklist lists domains with low reputation. Check your sending domain and every link domain.
DMARC aggregate reports. These show who is sending as your domain and whether authentication passes. Unexpected senders can hurt your domain. See our guide to reading DMARC aggregate reports.
Complaint data. Feedback loops like Yahoo’s CFL work at the domain level and only for DKIM-signed mail.

How to improve each kind of reputation

Improving domain reputation

Fix the list first. Domain reputation mostly reflects recipient reactions and list quality. Remove hard bounces, complainers, and long-term inactives.
Verify before importing. Run imported contacts through our free email verifier to remove bad syntax, nonexistent domains, disposable addresses, and typo domains. It checks DNS and known patterns; it doesn’t connect to the mailbox, so it can’t confirm every address is deliverable.
Split streams by subdomain. Use something like news.example.com for marketing and mail.example.com for transactional mail, so problems in one stream don’t spread. Our post on why you should not send from your root domain has details.
Align everything. Make DKIM d=, Return-Path, and link domains match your From: organizational domain.
Don’t switch to a lookalike domain to escape a bad reputation. M3AAWG says using cousin domains to get mail delivered when your main domain has reputation issues is what spammers do and is viewed negatively by mailbox providers.

Improving IP reputation

On a shared IP, your options are limited: improve your own sending (so you’re not the problem) and ask your ESP about pool quality.
On a dedicated IP, keep volume steady, warm up new IPs gradually, and get delisted from any blocklist after fixing the cause. Our email warm-up guide covers the ramp.
Set correct reverse DNS. Google requires that the sending IP have a PTR record resolving to a hostname that resolves back to the same IP.

Whether you need your own IP at all is a separate question, covered in shared vs dedicated IP for email.

FAQ

Is domain reputation more important than IP reputation?

For most senders today, yes. Authentication lets providers tie mail to your domain reliably, and domain reputation follows you across ESPs and IPs. IP reputation still matters for blocklists, throttling, and dedicated-IP senders, so you need both to be healthy.

Can I fix a bad domain reputation by changing IP addresses?

No. The domain’s history comes with you to the new IP, and a new IP without history adds its own warm-up risk. Fix the sending practices that caused the problem, then rebuild with your most engaged recipients.

Does a new domain start with a good reputation?

No. M3AAWG describes a new domain’s reputation as usually starting out unknown, which providers treat with similar caution to a bad one. You build reputation through a gradual warm-up with engaged recipients.

Do subdomains have their own reputation?

Providers can track subdomains separately, which is why splitting marketing and transactional mail onto different subdomains helps. The parent domain’s reputation can still influence them, so a subdomain is not a way to hide from a bad organizational-domain history.

Domain Reputation vs IP Reputation: What Matters More for Email