Which email blocklists are most important for deliverability and how should they be prioritized?
Summary
What email marketers say11Marketer opinions
Email marketer from Email Marketing Forum shares to prioritize blocklist monitoring based on your target audience. If you primarily send emails to users in Europe, focus on lists that are commonly used by European ISPs and mailbox providers. Tailor your monitoring efforts to the regions and industries you serve.
Email marketer from Litmus says blocklists are like a giant blacklist for IP addresses and domains that have been associated with spam. If you land on one, your emails might not make it to the inbox.
Email marketer from Reddit suggests focusing on major blocklists like Spamhaus, Barracuda, and URIBL. These lists are widely used and can significantly impact your deliverability. Don't waste time on obscure lists with little impact.
Marketer from Email Geeks explains that the importance of any RBL depends on how many of your recipients' mailbox providers implement it. For instance, being listed on Nosolicitado is harmful if your recipients are in South America, but not if they are in Europe.
Email marketer from SendPulse Blog shares that the impact of a blocklist depends on the recipient's email provider. Major blocklists like Spamhaus and Barracuda Central have a broad impact, while smaller, niche lists might affect deliverability to specific regions or industries. Prioritize monitoring lists that are relevant to your target audience.
Email marketer from Deliverability Blog shares that using blocklist checks as part of a broader deliverability strategy is important. While blocklists are important, also consider sender reputation, authentication, and engagement metrics to ensure consistent deliverability.
Email marketer from GlockApps Blog suggests proactively monitoring key blocklists such as Spamhaus, Barracuda, and Proofpoint. These lists are widely used by mailbox providers and security vendors to filter spam. Regularly checking your IP address and domain against these lists can help identify and address deliverability issues before they escalate.
Email marketer from ZeroBounce details maintaining clean lists, monitoring sender reputation, and authenticating your email (SPF, DKIM, DMARC) are key to avoiding blocklists. These practices show you’re a legitimate sender.
Email marketer from Mailjet Blog emphasizes the importance of monitoring blocklists to maintain a good sender reputation. Being listed on a blocklist can significantly impact deliverability, leading to emails being marked as spam or blocked entirely. Monitoring helps identify and resolve issues quickly.
Marketer from Email Geeks shares if a blocklist affects deliverability for more than a few recipients, it's a priority. Lists like RFC-ignorant, may warrant contacting the MX operator to explain the high probability of false positives. Proactive monitoring should include Spamhaus, Barracuda and Proofpoint.
Email marketer from StackExchange suggests using multiple tools and services to monitor blocklists. No single tool covers every list, so using a combination provides a more comprehensive view of your blocklist status.
What the experts say7Expert opinions
Expert from Email Geeks shares to meaningfully query the DBL (or URIBL), you need access to the content of mail being sent, which is more useful for ESPs.
Expert from Word to the Wise shares solely focusing on blocklists is not enough for deliverability. A broader perspective, including engagement and sender reputation, is necessary to achieve consistent inbox placement, as some lists are poorly managed.
Expert from Email Geeks shares domain-based lists are more interesting because a customer's content triggering one indicates a need to investigate the customer. IP-based hits are a sign that a customer is bad, after all other signs have been missed.
Expert from Email Geeks explains some blocklists are not publicly available and you can only know you're on them if mail is actually blocked.
Expert from Spam Resource explains blocklists should be used as a diagnostic tool, not a definitive judgment of sending practices. Being listed can indicate underlying issues that need attention, such as list hygiene problems or compromised accounts.
Expert from Email Geeks notes that dedicated IP listings may indicate the customer is sending mail to recipients who didn't ask for it, pointing to problematic behavior. Reputation providers may then analyze content (hostnames) to identify similar bad content elsewhere.
Expert from Email Geeks says being listed on Spamhaus will directly damage delivery, while being listed on SURBL correlates with poor practices that lead to poor delivery.
What the documentation says5Technical articles
Documentation from URIBL explains their lists categorize URLs found in spam. Some lists focus on new or potentially malicious domains, while others flag URLs associated with phishing or malware. Understanding these categories is useful for identifying compromised content.
Documentation from Barracuda Central details the Barracuda Reputation Block List (BRBL) is a real-time database of IP addresses with poor reputations. It is used by Barracuda Networks' email security products to identify and block spam. If you find your IP address on the BRBL, it indicates that your sending practices need improvement.
Documentation from Microsoft discusses their sender support space. If you are having trouble sending emails to Microsoft users, their documentation provides information on their policies and best practices for ensuring deliverability. This is crucial for any sender targeting Outlook.com or Hotmail users.
Documentation from Spamhaus explains Spamhaus maintains several blocklists, each with a specific purpose. The SBL (Spamhaus Block List) lists IP addresses of known spam sources, while the DBL (Domain Block List) lists domains found in spam. Understanding the differences between these lists is crucial for effective troubleshooting and delisting.
Documentation from Proofpoint describes the Proofpoint Dynamic Reputation Filter (DRF) uses real-time analysis of email traffic to identify and block spam. It assesses sender reputation based on various factors, including sending volume, content, and engagement metrics. Being listed on the DRF can significantly impact deliverability to organizations using Proofpoint's email security solutions.