How do you contact ISPs to get off email blacklists?
Matthew Whittaker
Co-founder & CTO, Suped
Published 8 Aug 2025
Updated 15 Aug 2025
4 min read
Finding your domain or IP address on an email blacklist, also known as a blocklist, is never a good sign. It can severely impact your email deliverability, meaning your legitimate messages might end up in spam folders or be rejected entirely by recipient mail servers. When this happens, a critical step is understanding how to contact Internet Service Providers (ISPs) and other email service providers to request delisting.
The process can sometimes feel like navigating a maze, especially with the varied approaches different ISPs and blocklist operators take. However, with the right information and a systematic approach, it is possible to get your sending reputation back on track.
Before you can contact an ISP or blocklist operator, you need to confirm that you are, in fact, listed and understand why. Email bounces often provide clues, but a dedicated check is more reliable.
Checking for a blocklist listing
Start by using a reliable blacklist checking tool. These tools scan your IP address or domain against numerous public blocklists (or blacklists) like Spamhaus, SpamCop, and Barracuda. If you're listed, the checker will usually provide details, including the specific list and often a link to their delisting process. Private ISP blacklists are harder to identify directly, often only becoming apparent through bounce messages.
Understanding the reason for your listing is paramount. Common causes include sending to spam traps, high complaint rates, sudden volume spikes, or compromised accounts. Without addressing the underlying issue, even if you get delisted, you're likely to end up back on a blacklist (or blocklist) very quickly.
Before you initiate contact, it's crucial to prepare your case. This involves not only identifying the problem but also demonstrating that you've taken corrective actions to prevent future issues. ISPs and blocklist operators want to see that you are a responsible sender committed to good practices.
Essential steps before delisting requests
Before reaching out, ensure you have addressed the root cause of the blocklisting. This might involve cleaning your email lists, implementing stronger email authentication protocols, or addressing security vulnerabilities if your system was compromised. Demonstrating these proactive steps can significantly strengthen your delisting request. For a detailed understanding, refer to our guide on DMARC, SPF, and DKIM.
Review logs: Analyze your mail server logs to identify any unusual sending patterns or suspicious activity that might have led to the listing.
Clean your lists: Remove unengaged subscribers, hard bounces, and any known spam traps from your mailing lists. A clean list is fundamental for good deliverability.
Implement authentication: Ensure your SPF, DKIM, and DMARC records are correctly configured. These authentication methods verify your identity as a sender and are crucial for improving sender reputation.
Here's an example of a simple DMARC record that you might implement:
Such a record sends aggregate and forensic reports, helping you monitor email authentication outcomes.
Strategies for contacting ISPs
Once you've done your due diligence, the next step is to reach out to the relevant parties. This usually involves contacting the specific blacklist operator or the ISP directly. The method of contact can vary significantly.
For public blacklists (also blocklists), such as Spamhaus, you can often find a delisting request form or process directly on their website. These are typically straightforward, requiring you to input your IP address or domain and sometimes provide a brief explanation of the issue and corrective actions taken. Following their specific instructions is crucial for a successful removal.
Public blacklists
Process: Usually involves a clear web-based delisting form or a published email address for requests. Many have automated processes once the issue is resolved.
Information required: IP/domain, evidence of problem resolution, and a brief explanation.
Private ISP blacklists
Process: Often less transparent. May require finding a specific postmaster email address (e.g., postmaster@example.com) or even a phone call to customer support to be redirected to a technical team. Some ISPs, like AT&T or Outlook, have their own specific delisting forms.
Challenges: Getting past frontline support who may not understand email deliverability issues. Patience is key.
When an ISP postmaster is unresponsive, it can be particularly frustrating. In such cases, persistence is important. Try different contact methods if available, or consider if any bounce messages provide a more direct point of contact.
Sometimes, the lack of a clear point of contact can delay the delisting process considerably. Be prepared for a potentially lengthy process with some providers.
What to include in your delisting request
Your delisting request should be clear, concise, and professional. The goal is to provide the necessary information quickly so the operator can assess your case and, hopefully, remove your listing. A well-crafted request can expedite the process.
Information
Details to include
Your IP address/domain
Clearly state the IP address and/or domain that is currently listed.
Blocklist name
Specify which blacklist (or blocklist) you are listed on. For ISPs, mention their internal system if known.
Date of listing
Provide the approximate date when you first noticed the issue.
Root cause identified
Explain what you believe caused the listing (e.g., spam trap hit, compromised account, high bounces).
Corrective actions
Detail the steps you have taken to remedy the situation and prevent recurrence. This is the most crucial part.
Contact details
Provide a clear email address and phone number where they can reach you.
Always maintain a polite and respectful tone, even if you're frustrated. Remember, their job is to protect their users from unwanted email, and demonstrating that you're a legitimate sender who understands their policies will go a long way. Additionally, be patient. Delisting can take anywhere from a few hours to several days, depending on the blacklist and the ISP.
Views from the trenches
Best practices
Maintain comprehensive records of all communication with ISPs, including dates, times, and specific actions discussed.
Implement automated monitoring for your IP and domain on major blacklists to detect listings promptly.
Regularly audit your email sending practices to ensure compliance with best practices and industry standards.
Common pitfalls
Assuming that once delisted, the problem is permanently solved without addressing the root cause.
Becoming confrontational or impatient with support staff, which can hinder the delisting process.
Failing to document corrective actions, making it difficult to demonstrate compliance to blocklist operators.
Expert tips
If an ISP postmaster is hard to reach via public channels, try direct email addresses often found through DNS lookups or specific contact forms.
For persistent issues with unresponsive ISPs, consider reaching out via phone to general support and asking for escalation to a postmaster team.
Understand that some ISPs implement a 'persistence filter' through their support structure to weed out less persistent senders.
Expert view
Expert from Email Geeks says that it can take several attempts to connect with a support agent who understands the existence of a postmaster team and how to transfer a call without requiring a customer ID. Once connected, postmaster teams often dislike phone calls and may provide a direct email address, though some companies have a policy requiring an initial phone interaction.
2020-05-07 - Email Geeks
Marketer view
Marketer from Email Geeks says that companies providing no way to contact them except by phone, particularly when the issue involves transactional emails with no unsubscribe option, can be highly frustrating. It can take a long time to resolve such issues via phone support.
2020-05-07 - Email Geeks
Maintaining a clean sending reputation
Dealing with email blacklists (or blocklists) requires a methodical approach, starting with identification and root cause analysis, moving to corrective action, and finally, a well-prepared outreach to the relevant ISP or blocklist operator. It's a testament to the ongoing effort needed for email deliverability. Remember, getting off a blacklist is not just about the request itself, but about proving you are a trustworthy sender.
Continuous monitoring of your sending reputation and proactive management of your email lists and infrastructure are key to avoiding future listings and ensuring your emails consistently reach the inbox.
Spamhaus
0Spam
Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
TechTheft
Barracuda. If you're listed, the checker will usually provide details, including the specific list and often a link to their delisting process. Private ISP blacklists are harder to identify directly, often only becoming apparent through bounce messages.
Spamhaus, you can often find a delisting request form or process directly on their website. These are typically straightforward, requiring you to input your IP address or domain and sometimes provide a brief explanation of the issue and corrective actions taken. Following their specific instructions is crucial for a successful removal.
AT&T or 
Outlook, have their own specific delisting forms.
