False positives when checking domains against the Spamhaus SBL arise from a confluence of factors. These include unconventional uses of the SBL for checking domains, shared hosting environments where the actions of one user can impact others, the inheritance of dynamic IPs previously used for spam, sudden increases in email volume, the use of spam-like keywords, misconfigured DNS records, compromised websites sending unauthorized emails, inadequate IP warming procedures, temporary misinterpretations of traffic patterns by filters, and a lack of clear email identity (authentication and sending reputation). These situations often lead to legitimate emails being incorrectly flagged as spam.
9 marketer opinions
False positives when checking domains against the Spamhaus SBL can arise from various factors, including shared hosting environments where one user's spam activity affects others, the inheritance of dynamic IPs previously used by spammers, sudden increases in email sending volume or the use of spam-like keywords, IP reputation issues on shared servers, low reputation of new domains, misconfigured DNS records, compromised websites used for spam, and inadequate IP warming practices for new IP addresses. These scenarios often lead to legitimate emails being incorrectly flagged as spam due to circumstances beyond the sender's direct control.
Marketer view
Email marketer from SparkPost explains that if a new IP address is not properly warmed up before sending large volumes of email, ISPs may view this as suspicious activity and flag the IP, leading to a listing. This can occur even if the emails are legitimate.
25 Oct 2022 - SparkPost
Marketer view
Email marketer from Reddit mentions that dynamic IP addresses assigned by ISPs can sometimes be previously used by spammers. If a new user inherits such an IP, their emails might be blocked due to the IP being on the SBL, leading to a false positive.
21 Aug 2023 - Reddit
4 expert opinions
False positives when checking domains against the Spamhaus SBL can stem from various sources. Scarlet.be's unusual method of checking domains by resolving their IPs and comparing them to the SBL can lead to incorrect listings. Short-term blacklistings, where filters temporarily misinterpret traffic, also contribute to the issue. Finally, legitimate emails lacking clear identity markers such as proper authentication (SPF, DKIM, DMARC) and a consistent sending reputation may be incorrectly flagged as spam.
Expert view
Expert from Spam Resource explains that one cause of false positives is short-term blacklistings. These can occur when filters temporarily misinterpret traffic patterns or activity as malicious, leading to a brief period where a domain or IP is listed before being removed when the issue resolves itself or is corrected.
6 Mar 2022 - Spam Resource
Expert view
Expert from Word to the Wise explains that legitimate email can be marked as spam when it lacks a clear, verifiable identity. This includes proper authentication (SPF, DKIM, DMARC) and a consistent sending reputation. Without these, even non-spam content can be filtered due to looking suspicious to automated systems.
30 May 2023 - Word to the Wise
5 technical articles
False positives when checking domains against the Spamhaus SBL can arise from various factors. Legitimate servers can be temporarily compromised and used for spamming without the owner's knowledge, leading to listings based on observed behavior. Systems can misinterpret signs of malware distribution, phishing activity, or spam traps, and even network issues can be falsely identified as malicious. Spam detection mechanisms may misclassify legitimate emails based on algorithms and patterns, especially if the sending infrastructure is new and lacks reputation. IP addresses can be listed due to spam complaints, spam trap hits, or being part of a compromised network, with false positives occurring if spam activity is incorrectly attributed or if there's a delay in removing a listing. Finally, URL patterns in emails, particularly shortened or obfuscated URLs, can trigger spam filters and incorrectly flag legitimate emails.
Technical article
Documentation from HetrixTools.com shares that domains can be blocklisted because of malware distribution, phishing activity, spam traps, or a hacked website. False positives can occur because systems misinterpret these signs, and sometimes a network issue can be falsely identified as malicious.
22 Mar 2024 - HetrixTools.com
Technical article
Documentation from Cisco Talos says spam detection mechanisms can sometimes misclassify legitimate emails as spam based on algorithms and patterns. For example, if new sending infrastructure has no reputation, this can impact deliverability even if sending legitimate emails.
5 Dec 2022 - Talos Intelligence
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