What is the appropriate response time when reporting a client mailing from a stolen list to an ESP?
Michael Ko
Co-founder & CEO, Suped
Published 10 Aug 2025
Updated 19 Aug 2025
8 min read
Discovering that a client is mailing from a stolen list is a serious issue that demands immediate attention. When you, as a vigilant member of the email community, encounter such a situation and report it to an email service provider (ESP), the question of an appropriate response time from their end naturally arises. My goal is always to protect the integrity of the email ecosystem, and part of that involves understanding how quickly these matters are addressed.
The impact of a client using a stolen list extends far beyond just that particular sender. It can severely damage the reputation of the ESP, potentially leading to widespread email deliverability issues for all their legitimate clients. This is why a prompt and effective response from the ESP is not just a courtesy, but a necessity for maintaining healthy sender reputation metrics across their platform. Without swift action, an ESP (and its clients) can face significant challenges with inbox placement.
I often find myself navigating these complex situations, trying to balance the need for quick resolution with the understanding that ESPs have their own internal processes. However, certain types of abuse, like mailing stolen lists (especially those containing spam traps), require an expedited response. Let's delve into what constitutes an appropriate response time and the factors that influence it.
The critical role of timely reporting
When a client is caught sending to a stolen list, particularly one that includes known spam traps, the urgency for an ESP to act is paramount. Such activity not only violates terms of service but also poses an immediate threat to the ESP's IP and domain reputation. Spam traps are highly effective at identifying illegitimate sending practices, and hitting them frequently can result in rapid blocklisting of sending IPs and domains, affecting all clients using that infrastructure. This is why you must understand the consequences of a blacklisting event.
ESPs have a responsibility to their entire client base to maintain excellent deliverability. Allowing a single bad actor to continue operating can lead to their shared IPs (or even dedicated ones if reputation issues spread) being placed on major email blocklists (also known as blacklists). This can significantly reduce inbox placement rates for everyone, leading to lost revenue and customer dissatisfaction. For this reason, ESPs often have dedicated abuse desks or compliance teams to handle such reports.
My experience has shown that the faster an ESP acts, the less widespread the damage becomes. Quick action demonstrates to the reporting party, mailbox providers, and the wider email community that the ESP takes abuse seriously. This proactive stance helps them preserve their overall email deliverability rates and maintain trust with key industry players who rely on clean sending environments.
Factors affecting ESP response times
Several variables come into play when determining how quickly an ESP will respond to a report of a client mailing from a stolen list. These factors can range from the nature of the report itself to the internal operations of the ESP.
A crucial factor is the severity of the reported abuse. If the report indicates a large volume of mail from a stolen list, or if it involves active spam trap hits, it's likely to be prioritized over less severe issues. Another consideration is the ESP's existing relationship or history with the reported client. A client with a prior record of complaints or policy violations might face swifter action than a first-time offender.
The size and resources of the ESP's abuse or compliance team also significantly impact response times. Larger ESPs with dedicated teams and automated systems for handling abuse reports may be able to react more quickly than smaller providers with limited staff. Furthermore, if the client is new to the ESP and has a history of being kicked off other platforms for similar offenses, this information, if known or discoverable by the ESP, could also lead to a faster response. I've often seen how a problematic client's past behavior can influence an ESP's decision-making process.
Factor
Impact on response time
Severity of abuse
High impact incidents, like spam traps, typically trigger faster responses.
ESP team size
Larger abuse teams often have quicker processing times and more resources.
Client history
Repeat offenders or clients with known bad practices may be acted upon faster.
Reporting channel
Using the official abuse address can streamline the investigation process.
Recommended response windows and escalation paths
Given the potential for severe reputation damage, my general recommendation is that an ESP should acknowledge and begin investigating such a report within 24 business hours. This timeframe allows for initial assessment and internal communication without letting the problem escalate further. For critical issues like active spam trap hits, I'd hope for an even quicker response, ideally within a few hours, if the report is clear and actionable.
However, sometimes an initial response may just be an acknowledgment, not a resolution. As a reporter, you might still receive mail from the offending client even after notifying the ESP. The decision point then becomes whether to wait for the ESP to suspend the customer or take independent action, such as suppressing the spamtrap or forwarding the mail to blocklisting organizations. Many in the industry suggest giving the ESP at least 24 hours to take action before escalating on your end, as per standard customer service response times.
Immediate actions for the reporter
Document the incident: Keep records of the abusive mail, the report sent to the ESP, and any subsequent communication.
Suppress the spamtrap: If you continue to receive mail, suppress the spamtrap address from your end to prevent further hits.
Consider escalation: If the ESP is unresponsive after 24 business hours, escalate the issue to relevant blocklisting organizations or industry forums (e.g., Email Geeks). This might also involve expediting delisting for affected IPs.
If an ESP's abuse desk has a history of unresponsiveness, or if you know the client is a serial offender who has been kicked off other major ESPs like SendGrid for similar issues, the recommended waiting period might be shorter. In such cases, quicker escalation to relevant blocklists or anti-spam organizations may be justified to protect the wider email community. My priority is always to mitigate harm to the email ecosystem, and sometimes that means taking swift action when an ESP falls short.
Preventative measures and long-term strategies
To minimize instances of clients mailing from stolen lists, both ESPs and senders have proactive roles to play. For ESPs, this includes robust pre-vetting processes for new clients, especially those with high volume sending needs or suspicious past activity. Continuous monitoring of sending behavior for all clients is also crucial, using automated systems to detect anomalies that might indicate list abuse or compromised accounts.
ESPs should also have clear and accessible channels for abuse reporting. Making it easy for third parties and mailbox providers to report suspicious activity, and ensuring that these reports are routed directly to a responsive abuse desk (e.g., abuse@their-domain.com), is fundamental. A transparent process that includes automated acknowledgments and follow-up mechanisms can build trust and encourage more timely reporting from the community.
For senders, prevention is always better than cure. This means adhering strictly to consent-based list building practices, regularly cleaning email lists to remove inactive or problematic addresses, and implementing strong authentication protocols like DMARC, SPF, and DKIM. These measures not only improve deliverability but also make it harder for malicious actors to spoof your domain or steal your lists in the first place. Keeping an eye on your sender reputation and addressing any issues promptly can prevent many deliverability headaches down the line.
Conclusion
Ultimately, the appropriate response time for an ESP when a client is mailing from a stolen list is as swift as possible, ideally within 24 business hours, with immediate action for critical threats. This swiftness is not just about isolated incidents, but about upholding the integrity of the entire email ecosystem. By understanding the factors at play and maintaining open communication channels, we can collectively work towards a safer and more reliable email environment for everyone. It's about collective responsibility and a shared commitment to healthy sending practices.
Views from the trenches
Best practices
Always use the official abuse desk email for reporting to ensure it reaches the right team quickly.
Include all necessary details in your initial report: headers, timestamps, and evidence of the stolen list.
Follow up professionally if you don't receive an initial acknowledgment within a few hours.
Understand that ESPs need time to investigate, but push for urgency with clear evidence.
Maintain your own records of reports and communications for future reference and accountability.
Common pitfalls
Expecting an immediate suspension without providing sufficient evidence or context to the ESP.
Not giving the ESP enough time to respond before escalating to blocklists, which can strain relationships.
Assuming all ESPs have the same response capabilities or abuse desk sizes.
Failing to track your own spam traps and their hits, which are critical indicators of abuse.
Not having a clear internal process for handling abuse reports you receive yourself.
Expert tips
If the client is a known serial abuser, mention their history with other ESPs in your report.
For smaller ESPs, be more understanding of response times, but still hold them accountable for action.
Consider shared industry platforms or groups for reporting if direct ESP channels are consistently unresponsive.
Automate detection of spam trap hits on your end to trigger immediate internal suppression actions.
Regularly review your own email security protocols, including DMARC and SPF, to prevent list theft.
Marketer view
A marketer from Email Geeks says they sent a heads-up to an ESP about a client mailing a stolen list that contained one of their spamtraps. They offered a warning because the address is shared with various blocking organizations that could lead to DNSBL listings.
2020-08-05 - Email Geeks
Marketer view
A marketer from Email Geeks says they received mail from the customer even after reporting, prompting them to consider whether to give the ESP more time or directly suppress the spamtrap and forward to other lists.
pre-vetting processes for new clients, especially those with high volume sending needs or suspicious past activity. Continuous monitoring of sending behavior for all clients is also crucial, using automated systems to detect anomalies that might indicate list abuse or compromised accounts.
abuse@their-domain.com), is fundamental. A transparent process that includes automated acknowledgments and follow-up mechanisms can build trust and encourage more timely reporting from the community.
