Why are my emails bouncing and is my sending IP on the SORBS spam blocklist?

Key findings

• Selective impact: SORBS is not universally used by all mail servers or internet service providers (ISPs), meaning its impact on email deliverability might be limited to a subset of your audience. Some senders may see only a 2-5% impact from a SORBS listing, particularly in B2B contexts.
• Correlation over causation: A listing on SORBS often indicates broader issues with sending practices. Even if SORBS itself does not cause widespread blocks, the behaviors that led to that listing (such as poor list hygiene or sending to spam traps) are likely to trigger other, more impactful blocklists and deliverability problems. This highlights the importance of addressing the underlying issues rather than just focusing on a single blocklist entry.
• Bounce message details: Many times, the specific blocklist causing a bounce will be explicitly mentioned in the bounce message itself. This makes the bounce message a critical first step in diagnosing why your emails are bouncing.
• Persistence of listings: A SORBS listing can persist for a long time, potentially years, before it begins to actively block emails at specific domains. This underscores the need for continuous blocklist monitoring.

Key considerations

• Analyze bounce messages: Before panicking about a specific blocklist, always examine the bounce messages for specific reasons and mentions of the blocking entity. The bounce message is your primary source of diagnostic information.
• Understand the true cause: A SORBS listing is often a symptom, not the root cause, of your deliverability issues. Focus on identifying and resolving the underlying sending practices that led to the listing, such as poor list acquisition, high complaint rates, or spam trap hits.
• Check for shared IP impact: If you are sending through a service provider that uses shared IP addresses, a listing might be due to the actions of another sender sharing your IP, rather than your own sending behavior. Understanding why your IP address is blacklisted is important.
• Proactive monitoring: Regularly check your sending IP and domain against various blocklists. While SORBS may have limited impact, other lists can severely affect deliverability. Utilize tools like online blacklist checkers to stay informed.

Key opinions

• Volume sensitivity: Marketers sending high volumes of promotional email, especially around holidays, are particularly susceptible to issues that could lead to blocklist listings, including SORBS. The increased sending volume can amplify any underlying issues.
• Diagnostic importance: The immediate reaction to bounces is often to check blocklists, but marketers acknowledge that the actual rejection message from the receiving server is the most important diagnostic tool. This message specifies who is blocking and why.
• Limited direct impact: Some marketers observe that SORBS itself may not be the primary cause of widespread blocks. Rather, it is used by specific domains, leading to targeted rather than global deliverability issues.
• Shared IP risks: If using shared IPs, marketers recognize that their deliverability can be impacted by the sending practices of other users on the same IP. This adds a layer of complexity to diagnosing bounce issues, as explored in articles like why am I getting soft bounces.

Key considerations

• Focus on the bounce message: Always prioritize reviewing the bounce message to understand the exact reason for rejection and which ISP or filter is causing the bounce. This information is more actionable than a general blocklist check.
• Proactive list hygiene: Given the risk of spam trap hits and complaints, marketers should maintain rigorous list hygiene practices. This includes regularly cleaning lists, removing inactive subscribers, and implementing robust consent processes.
• Understand ISP specific bounces: If bounces are specific to certain ISPs (like those seen with Optonline and other ISPs), investigate their specific filtering mechanisms and how they interact with blocklists like SORBS.
• Delisting processes: If a listing is confirmed to be causing bounces, understand the process for email blacklist removal for that specific blocklist.

Key opinions

• Limited adoption: Experts generally agree that SORBS is not as widely used by major email providers to block mail as some other blocklists (blacklists). This means its direct impact might be less severe than initially perceived by senders.
• Indicator, not sole cause: A SORBS listing is frequently a symptom or a correlating factor rather than the sole cause of widespread email blocks. The practices that lead to a SORBS listing (e.g., sending to spam traps, poor consent) are very likely to cause issues with other, more impactful blocklists and general inbox placement. This is a common point of discussion, as seen in how severe is a SORBS listing impact.
• Diagnostic priority: The most critical step when facing bounces is to examine the actual rejection message received from the recipient server. This message provides concrete evidence of who is blocking and the specific reason, rather than relying on general blocklist lookups.
• Spam trap data sharing: SORBS does share a subset of its spam trap data with corporate entities, suggesting that a listing could lead to issues with services that subscribe to that data feed. This creates indirect impacts beyond direct SORBS lookups.

Key considerations

• Don't panic over 'idiot lookup sites': Experts caution against panicking simply because an IP appears on a blocklist via a generic IP lookup tool. These tools often show listings on less impactful RBLs. The focus should be on actual bounce messages and the specific RBLs cited by recipient servers.
• Prioritize rejection messages: The first step in any troubleshooting process should be obtaining and analyzing the exact rejection message. The second step is identifying which entity (ISP, spam filter) is rejecting the mail based on that message.
• Address underlying sending issues: If you are listed on SORBS, it's highly probable that your sending practices are problematic. Experts advise focusing on fixing the root causes, such as list quality, consent practices, and content relevance, to prevent future blocklist entries and improve overall deliverability. This aligns with advice found in how to deal with a SORBS listing.
• Consider the spam trap connection: If a SORBS listing accompanies spam trap hits, as discussed on Arik Yavilevich's blog, this points to poor list hygiene as a primary issue that needs immediate attention.

Key findings

• Purpose of blocklists: Email blocklists, including SORBS, are designed to identify and list IP addresses or domains associated with spamming, malware distribution, or other abusive email practices. They serve as a crucial tool for protecting recipients from unwanted messages.
• Listing triggers: Common triggers for blocklist inclusion include sending unsolicited commercial email, high complaint rates from recipients, hitting spam traps, operating open relays, or being compromised by malware. Understanding how your email address ends up on a blacklist is essential.
• DNS-based operation: Many blocklists, including SORBS, operate as DNS-based blocklists (DNSBLs). Receiving mail servers query these DNSBLs in real-time to check if an incoming IP or domain is listed before accepting the mail. This is detailed in what is a DNSBL and its effect.
• Remediation pathways: Documentation typically outlines the steps required for delisting, which often include stopping the problematic behavior, submitting a request, and sometimes providing evidence of remediation. The process varies by blocklist.

Key considerations

• Preventative measures: The best way to avoid blocklists is through preventative measures, including maintaining clean and opt-in email lists, sending relevant content, monitoring complaint rates, and implementing proper email authentication (SPF, DKIM, DMARC).
• Understanding blocklist types: Different blocklists (like SORBS) target different types of threats (e.g., spam, compromised servers, open relays). Understanding these distinctions, as outlined in a guide to the different types of email blocklists, helps in targeted troubleshooting.
• Regular reputation checks: Regularly checking your IP and domain status on key blocklists is essential, even if you are not experiencing immediate bounces. Early detection can prevent widespread deliverability issues. Documentation on what email blacklists are often supports this.
• Impact of spam traps: Many blocklists use spam trap data as a primary input. Documentation often highlights that hitting a spam trap is a strong signal of problematic list acquisition or hygiene, leading to immediate listing. For more, see spam traps: what they are.