Cloudmark CSI: Why Your IP Is Listed and How to Reset It

Cloudmark Sender Intelligence (CSI) is an IP reputation system run by Cloudmark, now part of Proofpoint, and used by ISPs, mobile carriers and Proofpoint's own filtering products. If your mail is bouncing with "Cloudmark" or "CSI" in the error, your sending IP's reputation has dropped, usually because of spam trap hits, spam complaints or a compromised machine or account. Fix whatever caused it, then have the IP's owner file a reset request through the CSI portal at csi.cloudmark.com.

For the general blocklist playbook, see We Got Blocklisted. For where Cloudmark sits among the lists that matter, see the blocklists overview.

What a Cloudmark CSI bounce looks like

There's no single format, because each receiver writes its own rejection. Two documented examples. Rackspace, which uses CSI data, rejects with:

554 5.7.1 ACL dns_rbl; Client host [203.0.113.7] blocked using
sa-ip4tset.blagr.emailsrvr.com=127.26.0.2 Cloudmark CSI. Please visit
https://csi.cloudmark.com/reset-request for more information on why
this message could not be delivered

Proofpoint Essentials, which applies CSI at the connection level, produces something like:

550 5.7.1 Service unavailable; client [203.0.113.7] blocked using
Cloudmark Sender Intelligence

The common thread is the name Cloudmark or CSI and, often, a link to the CSI portal. If you see either, this page is the right one.

Why Cloudmark lists IPs

Cloudmark's own description of CSI names the inputs it weighs:

• Spam trap hits. Addresses that never signed up for anything receiving your mail.
• User complaints. Cloudmark specifically mentions trusted "This is spam" reports from end users.
• Reverse DNS reputation. The reputation of the hostname your IP resolves to.
• The neighborhood. The reputation of the IP block your address sits in.
• Traffic patterns over time, which help it spot snowshoe sending (spreading volume across many IPs to stay under thresholds).

In practice that maps to a familiar set of causes, most likely first:

1. List quality. Old, purchased or scraped addresses carry traps and generate complaints. See why spam traps are a data problem.
2. A compromised account, server or web form sending spam from your IP without your knowledge.
3. Mail people didn't expect, such as a reactivation send to a long-dormant segment.
4. Shared IP neighbors. If you're on an ESP's shared pool or a hosting provider's shared server, someone else's mail may be the cause.
5. Weak reverse DNS or a bad neighborhood, such as an IP in a range with a history of abuse, or a generic rDNS name.

Don't expect Cloudmark to tell you which. Vircom, a Proofpoint Essentials partner, notes that Proofpoint may not be able to share details on why an IP was listed. M3AAWG's general guidance is the same: list operators often won't explain specific listings, so troubleshooting is on you.

How to reset a Cloudmark CSI listing

Cloudmark's portal frames this as a reset rather than a delisting. The reset clears the listing; it doesn't change the reputation signals that caused it. If the traps and complaints continue, the block comes back.

1. Confirm it's Cloudmark. Read the bounce text. Check whether the rejections come from many unrelated domains or from one receiver, and note the receiving domains and timestamps.
2. Find and stop the cause. Pause or cut back sending to your least engaged recipients. Look for anything sending from the IP that you didn't plan: compromised mailboxes, abused forms, a forgotten server. Remove the data sources that brought in bad addresses.
3. Check your basics. Make sure the IP has a forward-confirmed reverse DNS name that matches your HELO hostname, and that SPF, DKIM and DMARC pass. The email checker covers authentication.
4. File the reset request as the IP's owner. Go to the CSI IP Reputation Remediation Portal at csi.cloudmark.com and complete the form. Vircom's guidance is that the IP owner, or the company actually using the IP, should file. Filing on someone else's behalf can leave you unable to complete the remediation steps.
5. Keep the reference ID. The portal issues one when you submit. If the block is in a Proofpoint Essentials environment, Vircom's instructions are to open a support ticket with that reference ID (or the IP, if you don't have one) after filing.
6. Resume slowly. Start with your most engaged recipients and watch bounces from the receivers that blocked you.

Cloudmark doesn't publicly document how long a reset takes, whether listings expire if you do nothing, or whether repeat resets are limited. Assume the first request is the one that needs to be credible.

If you're on a shared IP

If your mail goes through an ESP's shared pool, you can't file the reset; you don't own the IP. Send the bounce text to your ESP's support and let them work it. Then look honestly at whether your own sends could be part of the problem. See my ESP's shared IP is blacklisted for who owns what.

How to confirm it's fixed

Watch the receivers that were rejecting you. Rejections naming Cloudmark or CSI should stop. If they continue after the reset, either the reset hasn't propagated yet or the cause is still active, and continuing to push volume will make the second request harder. Recheck the portal before filing again.

How to keep it from coming back

• Remove traps at the source. Confirm new signups, validate addresses at the point of entry, and stop mailing people who haven't engaged in a long time.
• Keep complaints low. Clear unsubscribe, expected frequency, and no surprise sends to old segments.
• Monitor for compromise. Alert on unusual outbound volume from any IP or account you own.
• Watch bounces by receiving domain. CSI blocks tend to show up at specific ISPs and businesses, so a jump in one group of domains is your early warning.

If Proofpoint gateways are also rejecting your mail, see why Proofpoint is blocking your emails, since that's a related but separate process.

When to get help

If a CSI block keeps returning after resets, or it's showing up alongside listings on Spamhaus or other lists that matter, the underlying cause is usually in your data or infrastructure and worth an outside look. Get in touch.

FAQ

Is Cloudmark the same as Proofpoint?

Proofpoint acquired Cloudmark in 2017. Cloudmark's CSI data is used in Proofpoint products, but a Proofpoint gateway block can also come from Proofpoint's own reputation systems, which have their own removal process.

Can I check my Cloudmark reputation?

The CSI portal at csi.cloudmark.com is where Cloudmark handles IP reputation remediation. Your bounces are still the most reliable signal that CSI is actually affecting delivery.

Does Cloudmark charge to reset a listing?

Cloudmark's public material doesn't mention a fee, and legitimate blocklists don't charge for removal. Be wary of any third party offering paid Cloudmark delisting.

Why did my Cloudmark block come back after a reset?

The reset clears the listing, not the behavior. If your mail is still hitting traps or drawing complaints, CSI lists the IP again.