How do multiple or long links affect email deliverability?

Key findings

• Spam filter sensitivity: Spam filters are designed to detect suspicious patterns. Too many links can be interpreted as a characteristic of spam, particularly if combined with other problematic content or sender reputation issues. Mailgun, for instance, notes that emails with multiple links and no images may trigger spam filters.
• Reputation of linked domains: The reputation of the domains to which you link is critical. Including links to domains with a poor or unknown reputation can severely damage your own sender reputation and lead to blocklisting. This risk is amplified with a higher number of external links.
• URL length and complexity: While short, clean URLs are generally preferred, very long or complex URLs (often a result of tracking parameters or URL shorteners) can sometimes appear suspicious to filters, especially if they are heavily obfuscated or redirect multiple times. For more on this, see how URL length affects deliverability.
• Link tracking impact: Email service providers often wrap links for click tracking, which can significantly increase their length. While this is common practice, it's essential to understand its impact on the overall email content and how filters perceive these modified URLs. Read about HTTP tracking links and deliverability.
• Context is key: The impact of links is rarely isolated. It's evaluated within the broader context of email content, sender reputation, engagement metrics, and authentication protocols (like DMARC, SPF, and DKIM). A legitimate email from a trusted sender with many relevant links is less likely to be filtered than a suspicious email from a new sender with the same number of links.

Key considerations

• Quality over quantity: Focus on including only necessary and valuable links. Each link should serve a clear purpose for the recipient.
• Domain reputation: Ensure all linked domains (especially third-party ones) have a good reputation. Using a URL shortener that links to a malicious domain, for example, could put your email on a blocklist.
• Contextual relevance: Links should be relevant to the email's content and the recipient's expectations. Avoid misleading link text or hidden links.
• Testing: Regularly test your emails for deliverability, especially after making changes to link structures or content. This helps you identify potential issues before they impact your entire audience.
• Plain text version: Always include a well-formatted plain text version of your email. Some older spam filters may analyze this version more strictly, and excessively long URLs or too many links can look suspicious.

Key opinions

• Anecdotal impact: Many marketers report seeing a direct negative impact on deliverability when emails contain more than 10 links or links exceeding 120 characters, reinforcing that these factors are real concerns.
• Link reputation matters: A key concern for marketers is the underlying reputation of the domains being linked. Even if the sender's domain is good, linking to less-than-ideal domains can compromise deliverability, especially when many links are present. This is explored further in discussions about how hyperlinks affect deliverability.
• Tracking link length: Marketers note that email service providers' (ESPs) click tracking mechanisms can significantly lengthen URLs. While necessary for analytics, the resulting long links are a consideration for deliverability.
• Contextual risk: The danger of too many links is heightened when emails also lack images, as noted by Mailgun. Spam filters often assess content holistically, so a high link count combined with other red flags can be problematic.

Key considerations

• Optimize link count: Marketers should strive to minimize the number of links to only those essential for the email's purpose. This reduces the surface area for spam filter scrutiny and improves clarity for recipients.
• Monitor linked domains: It's crucial to regularly check the reputation of all domains linked in emails, especially third-party content. A single problematic link can affect the entire email's deliverability, leading to your domain being placed on a blacklist or blocklist.
• Evaluate URL shorteners: While convenient, URL shorteners introduce an extra layer of redirection and a new domain. Marketers should be cautious about using them, as they can negatively affect deliverability if not from a trusted source, as discussed by EasySendy. Consider how URL shorteners impact deliverability.
• Content balance: Aim for a balanced email content strategy, where links are integrated naturally within engaging text and visuals, rather than dominating the message. A good practice is to test your email's content using an email deliverability tester.

Key opinions

• Suspicious content signals: Experts believe that an unusually high number of links, particularly within a small email body, can serve as a strong indicator of spam or phishing attempts to automated filters.
• Reputation propagation: The reputation of linked domains is a critical factor. Experts emphasize that poor reputation from any linked domain can transfer negatively to the sender's reputation, regardless of the sender's own history. This underscores why third-party links affect deliverability.
• URL structure scrutiny: While link length itself isn't always a direct flag, extremely long or convoluted URLs, especially those with multiple redirects or suspicious-looking parameters, are more likely to undergo deeper scrutiny by spam filters. This includes concerns about URL length in an email href.
• Perceived value: Experts suggest that emails packed with links but lacking substantial, engaging content are often perceived as less valuable or more promotional, which can negatively influence filtering decisions.

Key considerations

• Balance and relevance: Ensure that the number of links is proportionate to the email's purpose and content. Every link should be relevant and add value to the recipient, rather than being included for the sake of it.
• Trustworthy domains: Only link to reputable and well-maintained domains. Avoid linking to sites with known security issues or questionable content, as this can lead to your emails being marked as spam or your domain being added to a blocklist.
• Transparent linking: Use clear, descriptive anchor text for your links. Avoid obfuscation or deceptive practices that could mislead recipients or filters. For example, link redirects affect reputation so ensure they're handled cleanly.
• Sender reputation first: A strong overall sender reputation can mitigate some of the risks associated with links. Focus on building trust through consistent sending practices, good engagement, and proper email authentication (SPF, DKIM, DMARC).

Key findings

• Content reputation factors: Documentation often includes links as a key component of overall content reputation. Issues like excessive links, or links to suspicious content, contribute to a negative content score.
• Spam trigger warnings: Many guides warn that a high link-to-text ratio, or the inclusion of suspicious links, can trigger spam filters. This implies that both quantity and quality of links are considered.
• Abuse patterns: Some documentation refers to known spam patterns, which can include a disproportionate number of links or overly complex, obfuscated URLs, indicating these characteristics are recognized by filtering systems.
• User engagement metrics: Documentation frequently stresses the importance of positive user engagement, which includes link clicks. If links lead to irrelevant or poor experiences, it can negatively impact sender reputation over time.

Key considerations

• Relevance and necessity: Documentation implies that every link in an email should serve a clear and relevant purpose for the recipient, contributing to the overall value of the message.
• Domain and URL reputation: Consistent advice from documentation is to ensure all linked domains (and the full URLs themselves) have a good reputation. Linking to untrustworthy sources can severely harm deliverability.
• Content balance: Maintain a healthy balance between text and links. Emails that appear to be nothing but a list of links are more likely to be flagged as spam.
• Proper formatting: Ensure links are correctly formatted and are not broken, as broken or malformed links can also raise flags with spam filters.