Email Blocklists

A blocklist is a published database of IP addresses or domains believed to send spam. Receiving mail servers query these lists during delivery and may reject, junk, or throttle mail from anything listed. A listing on a major blocklist can stop your mail cold at some providers.

What Blocklists Are

Blocklists (also called blacklists, DNSBLs, or RBLs) are run by independent organizations. Each has its own detection methods, listing criteria, and removal process. The ones you will encounter most:

Blocklist	Type	What it lists
Spamhaus SBL	IP	IPs with verified spam activity
Spamhaus XBL	IP	Compromised machines, botnets, open proxies
Spamhaus PBL	IP	IP ranges that should not send mail directly, such as residential connections
Spamhaus DBL	Domain	Domains seen in spam, including link and tracking domains
SpamCop	IP	IPs reported by users and spam traps
Barracuda	IP and domain	Reputation data from Barracuda firewall deployments
SORBS	IP	Spam sources, open relays, compromised hosts
URIBL / SURBL	Domain	Domains found in the body of spam messages

Note the distinction in the last column. Some lists track sending IPs. Others, like the Spamhaus DBL, URIBL, and SURBL, track domains that appear inside email content. Your domain can be listed even if every IP you send from is clean.

IP Listings vs Domain Listings

This distinction decides who fixes the problem.

IP listings target the server addresses mail is sent from. On Bento, you send from curated shared IP pools that Bento operates. If a pool IP gets listed, that is Bento's infrastructure and Bento's job to fix. See Sending Pools.

Domain listings target domains you own: your sending domain, your website, or your branded link tracking domain. Blocklist operators list domains based on what your mail contains and where your links point. Bento cannot delist a domain it does not own. Domain listings are yours to fix, with this guide.

	IP listing	Domain listing
What is listed	A Bento pool IP	Your sending, website, or tracking domain
Who fixes it	Bento	You
Typical cause	Another pool sender, or aggregate pool behavior	Your list quality, content, links, or a compromised site
Where to check	Bento monitors automatically	MXToolbox, Spamhaus checker

Which Lists Actually Matter

Not all blocklists are equal. Hundreds exist, and most are queried by almost nobody.

Spamhaus matters a lot. It is the most widely used blocklist family in the world. Major providers and countless corporate mail servers consult it. A Spamhaus SBL or DBL listing causes immediate, widespread delivery failure. Treat any Spamhaus listing as urgent.

SpamCop and Barracuda matter somewhat. They are used by a meaningful number of corporate and hosted mail systems. A listing causes partial delivery problems, mostly to business addresses.

URIBL and SURBL matter for domains. Content filters like SpamAssassin check them. A listed link domain raises spam scores even when your sending reputation is fine.

Most small lists do not matter. Lists like UCEPROTECT and dozens of obscure DNSBLs show up scary-red in blocklist checkers but are barely used by real mail servers. Some charge for removal, which reputable lists never do. Do not pay for delisting, and do not panic over a listing on a list nobody queries.

How to Check

Check your domains, not Bento's IPs. Bento monitors its pool IPs continuously.

1. Run your sending domain through the MXToolbox blocklist check. It queries dozens of lists at once.
2. Run your link or tracking domain through the same check. Content-based lists like the Spamhaus DBL often hit tracking domains.
3. Check the Spamhaus IP and Domain Reputation Checker directly. It shows the specific list, the reason category, and the removal path.
4. Read results with the previous section in mind. A Spamhaus or SURBL hit is urgent. A hit on an obscure list usually is not.

If delivery problems are concentrated at one provider, also check the bounce messages in Bento. Rejections often name the blocklist in the SMTP response. See the Bounce Guide for how to read them.

What Bento Handles

Bento operates the sending infrastructure, so IP-level blocklist work is handled for you:

• Continuous monitoring. Bento monitors its shared pool IPs against major blocklists.
• Delisting management. When a pool IP is listed, Bento works the delisting process with the blocklist operator.
• Pool health. Bento rotates and maintains IPs so that pool reputation stays strong, and curates which senders share each pool. See Sending Pools.

This means an IP listing rarely requires anything from you. If you believe a pool issue is affecting your delivery, contact support with the bounce messages you are seeing.

What Bento does not control is your domains. The rest of this guide covers domain listings.

What Causes Domain Listings

Domain blocklists list you because of what your mail does, not who sends it. Common causes:

• Spam trap hits. Sending to recycled or pristine trap addresses signals poor list sourcing. Traps come from old lists, purchased lists, and scraped lists. See Spam Traps.
• High complaint rates. Sustained complaints feed the data many blocklists use. See Spam Complaints and Feedback Loops.
• A compromised website. If your site is hacked to host phishing pages or malware, your domain gets listed fast, and the listing follows every email that links to it.
• Bad links in your email. Linking to flagged third-party domains, or using shared shorteners, can get your own domain associated with spam content.
• Snowshoe patterns. Spreading sends across many lookalike domains to dodge filters. Blocklist operators detect this and list the whole set.

Requesting Delisting

Fix the cause first. Every reputable blocklist rechecks after removal, and a delisting request without a fix leads to a fast relisting, which is harder to remove.

1. Identify the cause. Use the listing detail page. Spamhaus tells you the category and often the evidence window.
2. Fix it. Clean the list source, remove the bad links, secure the compromised site, or stop the send pattern that triggered the listing.
3. Submit the removal request:
   • Spamhaus: Use check.spamhaus.org, look up your domain, and follow the removal workflow for the specific list (SBL, DBL, and so on). Removals are free.
   • SpamCop: Listings expire automatically, usually within 24 to 48 hours of the spam reports stopping. No request needed in most cases.
   • Barracuda: Use the Barracuda removal form. Free, usually processed within a day.
   • SURBL / URIBL: Each has a lookup page with a removal contact or form. Explain what was fixed.
4. Be honest in the request. Blocklist operators read these constantly. Describe what happened and what changed. Vague or copy-paste requests get ignored.
5. Wait for propagation. After removal, receiving servers may cache the old answer for a few hours.

Never pay for delisting. Reputable lists do not charge. Lists that demand payment are not worth being delisted from because almost no one uses them.

Avoiding Relisting

A second listing is treated more skeptically than the first. Keep the conditions that caused it from coming back:

• Only import permission-based lists, and validate old segments before mailing them. See the Import Guide and List Hygiene.
• Use double opt-in for signup sources you do not fully trust.
• Keep complaint rates under 0.1% and watch for spikes. See Complaints.
• Keep your website patched and monitored. A compromised site is the most common cause of repeat domain listings.
• Keep DNS authentication verified so your legitimate mail is clearly identified. See DNS Setup.
• Avoid URL shorteners and links to domains you have not checked.

If a listing already pushed your mail into spam folders, pair this guide with the Spam Recovery Guide to rebuild placement after delisting. For the full deliverability picture, start at the Deliverability Guide.