How do internal email addresses get on purchased lists?

Internal email addresses often end up on purchased lists through a combination of public web scraping, data breaches (either directly from your systems or a partner's), guesswork based on common email patterns, or the illicit sale of event attendee lists. Even if an address is only used internally, it can be exposed through these channels.

What are the risks of using purchased email lists for marketing?

Using purchased lists can lead to legal penalties under anti-spam laws like CAN-SPAM or GDPR. It also severely damages your sender reputation, resulting in high bounce rates, increased spam complaints, and your emails being blocked or sent to spam folders by ISPs. This can also lead to your domain or IP being added to an email blocklist (or blacklist) .

How can I protect my internal email addresses from being added to purchased lists?

While complete prevention is difficult, you can minimize exposure by auditing where your internal addresses appear publicly, securing internal systems against breaches, educating employees on data sharing, and using contact forms instead of direct email listings on websites. Implementing strong email authentication ( SPF, DKIM, DMARC ) can also protect your domain from misuse.

Can I use an Email Service Provider (ESP) to send to a purchased list?

No, sending to purchased lists violates anti-spam policies of most legitimate Email Service Providers (ESPs). ESPs prioritize consent-based marketing to maintain good deliverability for all their users. Attempting to upload or send to a purchased list through an ESP can result in account suspension or termination, as well as significant deliverability issues.

How do internal email addresses get added to purchased lists? - Compliance - Email deliverability - Knowledge base

It's a frustrating experience to receive unsolicited emails from list vendors, especially when those emails are addressed to internal email addresses that are not widely published. We often wonder how these seemingly private addresses, like abuse@yourdomain.com or postmaster@yourdomain.com, end up on purchased email lists. This isn't just an annoyance, it can be a significant indicator of compromised data or aggressive, non-compliant data collection practices by these vendors.

The core issue often stems from how these lists are compiled. Unlike legitimate email marketing, which relies on explicit consent and opt-ins, purchased lists are typically scraped, harvested, or acquired through questionable means. This can involve anything from public web scraping to dark web data breaches. When internal addresses appear on such lists, it signals that your organization's data, or the data of those you interact with, has been exposed or improperly collected.

The unfortunate reality is that purchased email lists are often populated through methods that disregard privacy regulations and email best practices. This practice not only puts your brand's reputation at risk but also exposes your email infrastructure to significant deliverability challenges, including hitting spam traps and being placed on email blacklists.

This guide explores the common ways internal email addresses find their way onto purchased lists and highlights the severe implications of using such lists for your email marketing efforts.

How email addresses are harvested

One of the primary ways internal email addresses, especially generic ones like info@, sales@, support@, abuse@, or postmaster@, end up on purchased lists is through simple guesswork combined with public information. Many companies publicly list contact information on their websites, press releases, or through services like WHOIS. Scrapers, often automated bots, crawl the internet for email address patterns, even if those addresses are not explicitly advertised for marketing purposes.

Another common source is data breaches or compromised systems. If a client, partner, or even your own internal system (like an old CRM or marketing automation platform) suffers a data breach, those contact lists, including internal email addresses, can be siphoned off and sold on the dark web or to unscrupulous list brokers. Once this data is out, it can be repackaged and resold multiple times.

Event attendee lists are a notorious example. While some events may have legitimate opt-in processes for sharing information with sponsors, many list vendors operate without consent, illegally harvesting attendee contact details from public registrations, social media, or even directly from event organizers who may not be aware their data is being misused. If your internal email address was used for an event registration, even for a non-marketing purpose, it could be swept into these databases.

Some businesses also engage in what's known as email harvesting through less obvious means, such as appending email addresses to known company domains from publicly available data. For instance, if your name and company are public, a vendor might guess your email address pattern (e.g., firstname.lastname@yourdomain.com) and add it to their database, hoping for a valid hit.

Why internal email addresses are a particular concern

The appearance of your internal email addresses on purchased lists, especially those specifically used for compliance or technical purposes, is a clear red flag. These addresses, like abuse@ and postmaster@, are often monitored for internal purposes and are generally not intended for marketing communications. Their presence on a purchased list indicates that the list vendor likely obtained them through non-consensual means, rather than legitimate opt-in processes.

The fact that even obscure internal addresses are targeted highlights the extensive and often intrusive methods used by these list providers. It implies a disregard for data privacy and consent, which are foundational principles of ethical email marketing and deliverability. This can also mean that the list includes spam or fake email addresses that can severely impact your sender reputation.

If you receive emails to these internal addresses from a list vendor, it’s not necessarily a sign that you did anything wrong. Instead, it’s a symptom of a problematic ecosystem where data is often acquired and sold without proper authorization or consent. My experience suggests that it's just a part of dealing with unscrupulous vendors who scrape data indiscriminately.

Risks and consequences of using purchased lists

Using purchased email lists, regardless of how they were compiled, carries significant risks. The primary concern is compliance with anti-spam laws like the CAN-SPAM Act in the U.S. or GDPR in Europe. These laws generally require explicit consent from recipients before you send them marketing emails. Sending to a purchased list almost guarantees that you're violating these regulations, which can lead to hefty fines and legal repercussions.The FTC provides guidance on commercial email compliance.

Beyond legal issues, using purchased lists severely damages your email deliverability and sender reputation. Internet Service Providers (ISPs) and email clients closely monitor sender behavior. High bounce rates, low engagement, and increased spam complaints - all common outcomes of sending to purchased lists - signal to ISPs that you are a risky sender. This can lead to your emails being directed to the spam folder or even your domain or IP address being placed on an email blacklist or blocklist.

I often see businesses struggling to recover their email deliverability after sending to a purchased list. It’s a costly mistake that undermines all other legitimate email marketing efforts. The anti-spam policies of major ESPs, like Mailchimp (as discussed in the Slack thread), are designed to prevent the use of such lists because they harm the entire email ecosystem.

Furthermore, these lists are rarely effective for business goals. They consist of recipients who have not opted in and have no prior relationship with your brand. This leads to extremely low open rates, click-through rates, and conversion rates. It's a waste of resources and ultimately harms your long-term marketing strategy.

Protecting your internal email addresses

While you can't entirely prevent your email addresses from being guessed or appearing in a data breach, you can take steps to minimize the exposure of sensitive internal email addresses and protect your domain reputation. Regularly audit where your company's email addresses are published, both internally and externally.

Monitor your domain: Keep an eye on email blocklists to see if your domain or IP is listed, as this can indicate spam activity related to your addresses.
Secure internal systems: Ensure all your systems, including CRMs, HR software, and old databases, have strong security measures to prevent data exfiltration. Regularly update software and enforce strong password policies.
Educate employees: Train staff on phishing risks and the importance of not sharing internal contact information with unauthorized parties or signing up for newsletters using internal email addresses unless necessary.
Limit public exposure: Review your website, social media, and other public channels. Where possible, use contact forms instead of directly listing email addresses to make it harder for web scrapers to harvest them.

If you are concerned about your email addresses appearing on purchased lists, consider implementing more robust email security measures. This includes proper SPF, DKIM, and DMARC monitoring. While these won't stop your addresses from being scraped, they will protect your domain from being used for illegitimate purposes if your credentials are ever compromised.

Views from the trenches

Best practices

Maintain strong internal security protocols to protect all sensitive contact data within your organization.

Regularly audit your public-facing web properties and review event attendance policies for data sharing.

Use dedicated email addresses or contact forms for public inquiries instead of directly listing internal emails.

Implement email authentication protocols like SPF, DKIM, and DMARC for robust email security.

Common pitfalls

Assuming internal email addresses are immune to public scraping or data breaches, leading to lax security.

Engaging with list vendors or purchasing email lists, which can compromise internal addresses and reputation.

Failing to monitor your domain and IPs for blocklist (or blacklist) appearances after unsolicited contact.

Not educating employees about email security best practices and data sharing policies.

Expert tips

Consider using unique, trackable internal email addresses for event registrations to identify data sources.

Set up

spam trap

honeypots to identify and track list harvesting activities targeting your domain.

Marketer view

Marketer from Email Geeks says they get unsolicited emails from list vendors all the time, seeing it as a common issue for deliverability email addresses.

2019-10-22 - Email Geeks

Expert view

Expert from Email Geeks suggests that one of their clients might have been infected with something that stole their address book, leading to the internal email address being added to a purchased list.

2019-10-22 - Email Geeks

The path to better email deliverability

The unfortunate reality is that purchased email lists are never a good strategy for email marketing, and the presence of internal email addresses on these lists is a stark reminder of their unethical and often illegal origins. While it's impossible to completely shield every email address from public exposure or data breaches, understanding how these lists are created empowers you to take proactive measures.

Prioritizing consent-based list building and robust security practices remains the most effective way to protect your brand's reputation and ensure strong email deliverability. Focus on building an organic list of engaged subscribers who genuinely want to hear from you. This approach not only avoids legal and deliverability pitfalls but also yields far better marketing results.