What IP reputation actually means
IP reputation is the trust a receiving mail server places in the IP your mail comes from. There is no single global score. Every receiver builds its own view from a mix of signals, and the three that matter most are public blacklists, the technical setup of the IP, and each mailbox provider's private data about how its users react to your mail.
| Signal | Where it comes from | Visible in a one-off check |
|---|---|---|
| Blacklist status | Public DNSBLs like Spamhaus ZEN, Barracuda BRBL, SpamCop | Yes |
| Reverse DNS (PTR) | DNS record set by whoever owns the IP | In the email deliverability test and in monitoring |
| Gmail reputation | Google Postmaster Tools for your domain | No, needs your connected account |
| Outlook.com data | Microsoft SNDS for your IP range | No, needs your connected account |
| Complaints and engagement | Each provider's own users | No, partly visible through the provider tools |
What this check covers
When you enter an IP, we query it on 100+ DNS blacklists, including all three Spamhaus ZEN parts (SBL for spam sources, XBL for infected hosts and PBL for dynamic ranges that should not send mail directly). The result shows each list that has the IP, the reason code it returned and the removal steps.
The second signal to check is the PTR record, the reverse DNS name of the IP, and whether that name resolves back to the same IP (often called FCrDNS). A missing or generic PTR, like one that looks like 203-0-113-10.dynamic.isp.net, is a strong negative signal. Google requires all senders to have valid forward and reverse DNS for their sending IPs, and many corporate filters reject mail from IPs without a PTR. Enter your domain in the email deliverability test to check the PTR of your mail servers along with SPF, DKIM and DMARC, or use the steps below for a single IP.
How to check IP reputation manually
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1
Look up the PTR with
dig +short -x 198.51.100.25. You should get a hostname such as mail.yourcompany.com. -
2
Resolve that hostname with
dig +short mail.yourcompany.com Aand confirm it returns the same IP. - 3 Make sure the hostname your server uses in its HELO greeting matches or is close to the PTR name.
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4
Query the main blacklists by reversing the IP and adding the list zone, for example
25.100.51.198.zen.spamhaus.org. - 5 Sign in to Google Postmaster Tools and Microsoft SNDS to see the reputation those providers assign.
Reading the provider signals
Google Postmaster Tools shows your spam rate as reported by Gmail users, plus authentication and delivery error data for your domain. Since February 2024 Gmail asks bulk senders to keep the user reported spam rate under 0.3%, and ideally under 0.1%. Microsoft SNDS shows, per IP, whether traffic to Outlook.com looks normal, suspicious or spammy and how many spam trap hits it had. Yahoo provides its own sender data for senders who register with it.
These numbers are only visible to the owner of the domain or IP, which is why no public tool can show them for any IP you type in. In BlacklistMonitoring you connect these accounts once and the data appears next to your list results, with alerts when your spam rate crosses 0.1% or 0.3%.
Shared vs dedicated IPs
If you send through an email platform on a shared IP, you share reputation with the other senders on it. The platform manages that pool, and a listing on a shared IP is theirs to fix, but it still affects you. A dedicated IP gives you full control, but only works well if you send enough steady volume to build a reputation. Low volume senders often do better on a good shared pool.
New dedicated IPs start with no reputation at all. Warm them up by sending small, engaged volumes first and growing over a few weeks. Sending a large campaign from a cold IP is one of the fastest ways to land on a list.
How to improve a poor IP reputation
- Fix any blacklist listing at the source, then request removal. Our blacklist directory has steps for each list.
- Set a proper PTR record through your hosting or IP provider, matching your mail hostname.
- Remove unengaged and bounced addresses, and stop sending to purchased lists.
- Keep volume steady instead of sending large bursts.
- Make sure SPF, DKIM and DMARC pass for mail from this IP. Use the SPF checker to confirm the IP is covered.
Track reputation over time
Reputation changes daily. With IP blacklist monitoring, BlacklistMonitoring rechecks your IPs on 100+ lists, watches PTR records and, on Business and higher plans, pulls in Google, Microsoft and Yahoo signals with spam rate alerts. Scale adds monitoring of whole CIDR ranges, useful for teams running many sending IPs. See the pricing page for plan limits.
Frequently asked questions
How do I check my IP reputation?
Run the checker above to see blacklist status, then confirm reverse DNS with dig -x or the email deliverability test. For the private scores mailbox providers keep, sign in to Google Postmaster Tools and Microsoft SNDS, or connect them in a monitoring tool to see them in one place.
What is a good IP reputation score?
There is no universal score. A healthy sending IP is on no major blacklist, has a matching PTR record, shows normal traffic in Microsoft SNDS, and keeps a Gmail user reported spam rate under 0.1%.
How long does it take to fix a bad IP reputation?
Blacklist removals often take hours to a few days once the cause is fixed. Rebuilding trust with Gmail and Outlook takes longer, usually a few weeks of steady, low complaint sending.
Does a PTR record affect email deliverability?
Yes. Gmail requires valid forward and reverse DNS for sending IPs, and many filters reject or score down mail from IPs without a PTR or with a generic one. It is one of the simplest fixes with a large effect.
Can I check the reputation of a shared IP?
You can check its blacklist status like any IP, and its PTR with a reverse DNS lookup. Provider data such as Microsoft SNDS is only available to whoever controls the IP, so for shared IPs that is your email platform.