Every mail server that receives your message asks two questions before it looks at the content: how trustworthy is the IP address this came from, and is that IP on a blocklist? The first is IP reputation; the second is answered by real-time blackhole lists (RBLs, also called DNSBLs). This page explains both in plain terms, and what to do when a list names your IP.
Checking a listing, fixing the cause, SPF, DKIM and DMARC, and keeping your sending clean are covered step by step in Understanding Email Blacklist Management: A Complete Guide. Already listed? The short version is What to do if your email is blacklisted.
IP reputation is how much receiving mail servers trust the IP your mail comes from, built from volume, complaints, spam-trap hits and blocklist status. An RBL is a list of IPs seen sending spam, queried over DNS as each message arrives. Check your sending IP with MXToolbox or the list's own lookup, fix the cause, then request removal. On Domain India shared hosting the sending IP belongs to the server, so delisting it is done by our support team: open a ticket with the report.
1. What IP reputation is
Receiving servers, and big providers such as Gmail and Outlook.com in particular, keep a running score for every IP address that sends them mail. The score rises and falls with:
- complaints, when recipients click "Report spam";
- spam-trap hits, mail sent to addresses that never signed up for anything;
- bounce rates, mail sent to addresses that don't exist;
- volume patterns, such as a quiet IP suddenly sending thousands of messages;
- authentication, whether SPF, DKIM and DMARC pass;
- blocklist status on the public RBLs.
A poor score shows up as rejections such as 550 5.7.1 Service unavailable, client host blocked using … or 554 5.7.1 … rejected because of bad reputation, or as mail that is accepted but quietly filed in junk. Your domain has its own reputation too, so a clean IP does not fully rescue a domain that has been used for spam.
2. How an RBL works
An RBL is published through DNS so that any mail server can query it in milliseconds. To check the IP 203.0.113.25, the receiving server reverses the numbers and looks up a name inside the list's zone:
25.113.0.203.zen.spamhaus.orgNo answer means "not listed". An answer in the 127.0.0.x range means "listed", and the last number says why. The receiving server then rejects the message, or adds to its spam score, depending on how its owner configured it.
Many lists refuse queries sent through big public DNS resolvers and answer with an error code instead of a real result. If you test by hand with dig against a public resolver and get a strange 127.255.255.x answer, use the list's own website lookup instead.
3. The lists that matter in 2026
Not every list carries the same weight. A listing on a widely used list affects delivery to many providers; a listing on a small one may affect almost nobody.
| List | What it covers | Where to check |
|---|---|---|
| Spamhaus (ZEN, DBL) | The most widely used lists, for IPs and for domains in spam | check.spamhaus.org |
| Barracuda | Used by many companies running Barracuda filters | barracudacentral.org lookup |
| SpamCop | IPs reported by users for recent spam; entries expire when reports stop | spamcop.net lookup |
| UCEPROTECT | Levels 2 and 3 list whole IP ranges, not just your IP | uceprotect.net |
| Cisco Talos | Reputation score rather than a yes/no list | talosintelligence.com |
| Microsoft SNDS | Outlook.com data for IPs you control, such as a VPS | Microsoft's sender support site |
SORBS, which older guides still recommend, shut down in 2024; ignore any "listed on SORBS" result from an outdated tool. For a quick sweep of many lists at once, use MXToolbox's blacklist check or MultiRBL.
Some lists sell "express delisting". Paying is rarely necessary: fix the cause, use the free removal process, and many lists drop the entry on their own once the spam stops. Focus on the lists your recipients actually use.
4. Why an IP gets listed, and how to get it removed
The usual causes are a mailbox with a stolen password, a hacked website script sending mail, an unprotected contact form, or mail to old or bought lists. The fix is always in the same order:
- Read the bounce.It usually names the list and the IP that was checked.
- Confirm the listingwith the list's own lookup and read the reason it gives.
- Find and stop the cause.Change compromised passwords, clean the website, add a CAPTCHA to forms, stop sending to the bad list.
- Request removal, saying what you fixed, or let the entry expire where the list works that way.
- Watch for relistingover the next few days.
Delisting before you fix the cause only leads to a new listing. If the cause was a hacked site, work through the hacked-site checklist first.
5. Shared hosting, VPS and your IP
On Domain India shared hosting, mail leaves from the server's IP address, which other accounts share. You cannot request delisting of a shared server IP yourself. Open a ticket with the blacklist report or the bounce message, and our support team will investigate and handle the delisting. Support cannot change a shared hosting account's IP address; if you need your own IP, that means a VPS.
- Shared hosting is not built for bulk mail. Outgoing mail is limited to 200 messages per hour per account on Domain India cPanel servers and 1,000 per day on DirectAdmin. Send newsletters through a newsletter service and add it to your SPF record.
- On a VPS, the IP and its reputation are yours. You handle delisting yourself, and a new IP needs a gentle start: low volume, clean lists, SPF, DKIM and DMARC in place from day one. Whether outgoing port 25 and a custom reverse DNS (PTR) record are available on your VPS is something to confirm with support before you plan a mail server.
- Incoming mail is filtered too. Our cPanel servers check incoming connections against the Spamhaus and SpamCop lists and use greylisting, so a sender on those lists may be refused when writing to you.
If you can't reach your own website or mailbox from the office but it works on mobile data, that is not an RBL: your own IP has probably been blocked by the server firewall after failed logins. See how to tell if the firewall has blocked your IP.
Frequently asked questions
What is server IP reputation?
It is how much receiving mail servers trust the IP address your mail is sent from. It is built from complaint rates, spam-trap hits, bounces, sending patterns, authentication results and whether the IP appears on public blocklists.
What is an RBL or DNSBL?
A real-time blackhole list is a list of IP addresses seen sending spam, published through DNS. Receiving mail servers query it as each message arrives and reject or score mail from listed IPs.
How do I check if my server IP is blacklisted?
Find the sending IP in the Received headers of a message you sent, then check it with a multi-list tool such as MXToolbox's blacklist check, or with the list's own lookup page, such as check.spamhaus.org.
My Domain India shared hosting server IP is on a blacklist. What should I do?
Open a support ticket with the blacklist report or the bounce message. The sending IP is shared by the server, so delisting is handled by the Domain India support team, not by individual customers.
Can Domain India give my shared hosting account a different IP?
No. Support cannot change the IP address of a shared hosting account. If you need your own IP address, you need a VPS.
Does SORBS still matter?
No. SORBS shut down in 2024. A result from an outdated checker that still lists SORBS can be ignored; focus on widely used lists such as Spamhaus.
Ready to sort it out? Follow the complete blacklist guide, test your mail with How to test email deliverability, or open a support ticket with the report if our server IP is listed. Support is on 24/7 live chat, and tickets get a first response within 15 minutes.
Send us the blacklist report or the bounce message, and our support team will investigate and handle the delisting.
Open a support ticket