How to assess the impact of an unknown email blacklist on deliverability?

Key findings

• Actual impact: The primary indicator of a blacklist's importance is whether it's actively blocking your emails from reaching intended inboxes. If email delivery is not being affected, the listing may not be critical to your operations.
• Recipient base: Some lesser-known blacklists or blocklists may only be used by a limited number of internet service providers (ISPs) or specific domain hosts. Understanding your audience's email providers can help determine relevance. You can read more about how email blacklists actually work.
• Specific hosts: Certain blacklists might specifically target domains hosted by particular companies, such as Web.com or Network Solutions. If your mailing list does not include a significant percentage of such domains, the impact will be minimal.
• Monitoring delivery: Continuously monitoring your email delivery rates and bounce logs is essential. This data provides concrete evidence of whether a blocklist (or blacklist) is causing deliverability issues.

Key considerations

• Proactive monitoring: Regularly check your IP and domain against major blocklists, even if you don't immediately see delivery issues. This can help you identify potential problems before they escalate. Learn more in our guide to email blocklists.
• Bounce analysis: Pay close attention to bounce messages. They often provide specific reasons for email rejection, including references to the blocklist (or blacklist) responsible.
• Recipient list segmentation: Analyze your recipient list to determine if a significant portion of your audience uses the email providers or hosting services that are affected by the unknown blacklist. This helps prioritize your efforts.
• Focus on high-impact lists: Prioritize removal from widely used blacklists like Spamhaus or Spamcop, as these have a far greater impact on overall deliverability. As Inboxy points out, being on a blacklist means your emails are more likely to be blocked or sent to spam.

Key opinions

• Direct impact is key: Many marketers only consider a blacklist (or blocklist) significant if it's actively preventing their emails from reaching their target audience. If there are no noticeable blocks, the listing may not warrant immediate action.
• Limited reach: Some blacklists (or blocklists) are only used by a small number of mailbox providers or specific hosting companies. If your recipient list doesn't heavily feature these domains, the impact will be minimal.
• Data-driven decisions: Marketers emphasize relying on bounce logs and deliverability reports to confirm if a listing is actually causing problems, rather than speculating. This aligns with approaches to diagnose email deliverability issues.
• Building a case: When an unknown blacklist (or blocklist) is discovered, marketers often need to demonstrate its lack of impact to stakeholders by analyzing their recipient data against the affected domains.

Key considerations

• Audience composition: Understand which ISPs and hosting providers your subscribers use. If an unknown blacklist (or blocklist) primarily affects a segment you rarely email, its impact might be negligible.
• Focus on deliverability metrics: Instead of just checking blacklist (or blocklist) status, monitor your inbox placement rates, open rates, and bounce rates. These metrics provide a holistic view of your deliverability health. You can perform a deliverability test to assess this.
• Leverage tools: Use deliverability tools and analytics to spot patterns in bounces or suppressed emails. These insights can point to a specific blacklist (or blocklist) or ISP issue. As Outbound Master advises, tracking blocked sender status involves analyzing IP and domain-level blocklist standings.

Key opinions

• Performance-based assessment: Experts prioritize whether a blacklist (or blocklist) is actively causing mail to be blocked. If emails are still delivering as expected, the listing's severity for that sender is low.
• Relevance to recipients: A blacklist (or blocklist) is only relevant if it's employed by the mailbox providers or hosting companies to which you send emails. If your audience isn't impacted, the listing is not important for your mail stream.
• Avoid snarkiness: Experts stress that advice focusing on actual deliverability impact is not dismissive, but rather a practical guideline for assessing the true threat level of a given blacklist (or blocklist).
• Data validation: They suggest cross-referencing blacklist (or blocklist) listings with your own sending logs and deliverability metrics to validate any perceived impact. This is crucial for managing senders and identifying the cause during blacklisting.

Key considerations

• Bounce code analysis: Dig into your bounce codes. If a specific blacklist (or blocklist) is causing issues, you will see explicit bounce messages referencing it.
• Recipient domain analysis: Prioritize understanding if the domains you send to are known to use the obscure blacklist (or blocklist). This can involve looking up recipient domain MX records or talking to postmasters.
• Reputation focus: Maintain a strong sender reputation across the board through good list hygiene, authentication (SPF, DKIM, DMARC), and engaging content. This naturally mitigates the impact of most blacklists (or blocklists). Kickbox highlights that finding your IP or domain on a blacklist is bad news and preventative steps are crucial.

Key findings

• Categorization of blacklists: Documentation often distinguishes between public, widely-adopted RBLs (Real-time Blackhole Lists) and private, internal blacklists (or blocklists) used by individual ISPs or hosting providers. The latter often have a much narrower impact.
• Bounce message significance: Mail servers that block based on a blacklist (or blocklist) usually return specific bounce codes and messages that indicate the listing. The absence of such bounces implies a low or no impact.
• Focus on reputation: A strong overall sender reputation can often mitigate the effects of minor or obscure blacklist (or blocklist) listings, as major ISPs prioritize their own reputation systems. Read more about understanding your email domain reputation.
• Limited scope: Some blacklists (or blocklists) may only apply to specific types of mail (e.g., marketing vs. transactional) or specific geographic regions, further limiting their global impact.

Key considerations

• Monitor delivery logs: Reviewing your mail server logs for rejection messages, specifically those indicating a blacklist (or blocklist) hit, is the most direct way to assess impact.
• DNSBL query tools: Utilize DNS-based Blackhole List (DNSBL) query tools to check if your IP or domain is listed. However, these tools only confirm presence, not necessarily impact. You can check what happens when your IP gets blocklisted.
• Consult ISP postmasters: If you suspect an issue with a specific ISP, their postmaster pages often provide guidelines on how they handle blacklists (or blocklists) and common deliverability issues. Klaviyo's Help Center provides a useful reference on email deliverability best practices, including blocklists.