Summary
A SpamAssassin LONG_HEX_URI warning flags emails that contain unusually long strings of hexadecimal characters within a URI. This often occurs with email tracking links that embed extensive data (for example, recipient ID, campaign ID, timestamps) directly into the URL, making it quite lengthy and complex. While the warning is typically accurate in identifying such links, its direct impact on email deliverability is generally minimal when it's the only or primary spam flag an email receives.
Key findings
- Low score impact: The LONG_HEX_URI rule typically contributes a very low score to the overall SpamAssassin rating. While any score increase is theoretically undesirable, this particular warning alone is unlikely to push an email into the spam folder.
- Tracking links: This warning is commonly triggered by legitimate email tracking links used by many email service providers (ESPs). These links often include long strings of data for analytics purposes.
- Context matters: The true impact depends on the entire email's content, sender reputation, and other potential spam triggers. A low-scoring rule like LONG_HEX_URI is usually negligible in isolation.
- SpamAssassin variability: Each SpamAssassin instance has its own configured rules, scores, and thresholds, meaning the impact can vary slightly. You can learn more about how SpamAssassin rules affect deliverability.
Key considerations
- Overall score: Focus on the overall SpamAssassin score rather than individual low-scoring rules. A single LONG_HEX_URI warning typically isn't a red flag if other factors are good. Understanding the SpamAssassin scoring system is helpful.
- Deliverability impact: The relevance of SpamAssassin scoring for modern deliverability is evolving. While some B2B filters might be stricter, major ISPs increasingly rely on sender reputation and engagement metrics over static content filters. Learn how relevant SpamAssassin scoring is today.
- URL length and complexity: Excessively long or complex URLs can sometimes raise flags, but modern tracking systems often necessitate this. Understanding how URL length affects deliverability is important.
- Troubleshooting: If you are concerned, check for other SpamAssassin warnings that carry higher scores. These would be more impactful than a LONG_HEX_URI warning.
What email marketers say
Email marketers frequently encounter the LONG_HEX_URI warning, especially when using email service providers (ESPs) that employ extensive tracking in their links. Many marketers note that while the warning is present, it rarely causes significant deliverability issues on its own. Their experience suggests that this flag is more of an indicator of highly tracked marketing emails rather than a severe spam trigger.
Key opinions
- Common occurrence: Marketers frequently see the LONG_HEX_URI warning, particularly with emails containing tracking links.
- Low impact: Most marketers agree that this warning, in isolation, does not typically lead to emails landing in spam folders, unless other, more severe spam indicators are also present.
- Marketing indicator: The flag often signifies that an email is marketing-oriented due to detailed tracking, which some recipients might not desire.
- ESP limitations: It can be challenging or impossible to fix this warning if it's tied to an ESP's standard tracking mechanisms, as marketers have limited control over the generated URLs.
Key considerations
- Focus on overall health: Rather than obsessing over a low-impact warning, marketers should prioritize overall email hygiene, content quality, and hyperlink best practices.
- Specific triggers: Some marketers suggest there might be a specific combination of characters or a ratio within the URL that triggers the LONG_HEX_URI rule, rather than just length. For potential solutions, review how to resolve hexadecimal sequence errors.
- Testing approach: When testing emails, consider that transactional templates or API testing might display this warning more prominently, while actual campaigns may have different aggregate scores.
- SpamAssassin scores: Marketers should understand how a SpamAssassin score is calculated to assess the true risk.
Marketer view
Marketer from Email Geeks suggests that a SpamAssassin LONG_HEX_URI warning often points to links with tracking parameters. They noted that their email received this flag and it appeared to be referencing the tracking link.
Marketer view
Marketer from Email Geeks indicates that this warning is likely accurate in identifying hexadecimal URIs. In their experience, if the warning appeared, it was indeed triggered by such a link.
What the experts say
Email deliverability experts generally concur that the SpamAssassin LONG_HEX_URI warning, while technically a flag, contributes a very minimal score to an email's overall spam rating. They highlight that its presence is often unavoidable with modern email tracking and that its impact is negligible unless combined with other, more significant spam triggers.
Key opinions
- Low scoring rule: Experts emphasize that the additional points assigned for this flag are typically low within the SpamAssassin scoring system.
- Configurable instances: Every instance of SpamAssassin has its own configurable rule base, learning, and score thresholds, which can slightly alter the rule's impact.
- Transactional vs. Marketing: The rule can be triggered by both marketing and transactional emails if they use long tracking URLs. Learn more about why emails go to spam.
- Necessary for tracking: Long URL strings with hexadecimal characters are often a necessary byproduct of sophisticated email tracking, required for detailed analytics on opens, clicks, and user behavior.
Key considerations
- Rule specifics: The rule often combines multiple conditions, such as the length of hexadecimal characters (e.g., 128 characters) and the overall email body size. Explore more about how SpamAssassin rules affect deliverability.
- Average scores: While configurable, average scores for this rule typically range from 0.05 to 1.5, which is relatively minor compared to other spam flags.
- ISP awareness: Major email service providers are generally aware of how their tracking links interact with SpamAssassin rules. If the rule caused significant issues for many users, changes would likely be made. Learn about common spam filter mistakes.
- Holistic view: Deliverability is multifaceted. Even with a LONG_HEX_URI warning, technical solutions can boost rates. Consult our guide on technical solutions for email deliverability.
Expert view
Expert from Email Geeks states that the score for a LONG_HEX_URI flag is usually quite low. They confirm that this particular warning contributes minimal points to the overall SpamAssassin score.
Expert view
Expert from Email Geeks explains that each SpamAssassin instance has unique rule bases and thresholds. They note that configurations can vary, impacting how rules like LONG_HEX_URI are weighted.
What the documentation says
Official documentation and technical guides explain that SpamAssassin's LONG_HEX_URI rule is designed to flag URLs containing suspiciously long sequences of hexadecimal characters. This is often an indicator of obfuscation or malicious intent, though it can also be triggered by legitimate tracking parameters. The documentation typically details the precise conditions for triggering the rule and its default score.
Key findings
- Rule definition: The rule explicitly checks for patterns of hexadecimal digits within URIs that exceed a certain length threshold.
- Default score: Documentation typically assigns a relatively low default score to LONG_HEX_URI, reflecting its minor contribution to overall spam scores.
- Obfuscation indicator: The rule is primarily intended to identify URLs that might be attempting to hide malicious content or bypass filters through hexadecimal encoding. However, it can also catch legitimate, but long, tracking parameters.
- Conditional triggering: Some rule configurations might combine LONG_HEX_URI with other conditions, such as the overall email size, for more nuanced scoring.
Key considerations
- Rule weighting: The impact of any SpamAssassin rule, including LONG_HEX_URI, can be adjusted by server administrators. This means its actual effect can vary depending on the specific mail server's configuration.
- Email code analysis: While not directly an HTML error, highly complex URLs might sometimes appear alongside other code issues. Email code analysis reports can flag these.
- Malformed HTML: A LONG_HEX_URI warning typically indicates a URL structure issue, not necessarily malformed HTML itself. However, both can contribute to higher spam scores. Understand the impact of malformed HTML.
- Holistic filtering: Modern spam filtering systems use a combination of factors, including reputation, authentication (SPF, DKIM, DMARC), and engagement metrics, alongside content rules. The LONG_HEX_URI rule is just one small piece of a larger puzzle. You can find out more on Apache SpamAssassin rules here.
Technical article
Documentation from Apache SpamAssassin official site states that LONG_HEX_URI checks for long strings of hexadecimal characters within URIs. This rule is designed to identify potentially obscured or suspicious URLs.
Technical article
Documentation from a deliverability guide outlines that this rule usually carries a low numerical score. It explains that its contribution to the total spam score is generally minor compared to other rules.
Related resources
2 resources
Related pages
How to resolve SpamAssassin hexadecimal sequence errors
How do SpamAssassin rules affect deliverability?
How relevant is SpamAssassin scoring for modern deliverability?
How do multiple or long links affect deliverability?
How does URL length affect email deliverability?
How do hyperlinks in the body affect deliverability?
Why Your Emails Are Going to Spam
Boost Email Deliverability Rates: Technical Solutions
Email Deliverability Issues: Getting Messages to Inbox
