How do chained redirects affect email delivery and sender reputation?

Key findings

• Reputation Risk: Each domain in a redirect chain can carry its own sender reputation, and a poor reputation at any hop may negatively affect deliverability. This is particularly relevant for multiple or external domains used for tracking.
• ISP Scrutiny: Inbox providers (ISPs) and Mailbox Providers (MBPs) may mechanically follow redirect chains to assess the final destination and intermediate domains. This process can consume resources, and excessive or suspicious redirects might trigger spam filters, affecting email deliverability rates.
• Complexity and Trust: Overly complex or unfamiliar redirect chains can raise red flags with spam filters, potentially leading to emails being blocked or routed to the spam folder. Simplicity generally correlates with higher trust from filtering systems.
• Variable Behavior: The extent to which providers analyze redirect chains varies. Enterprise filters often perform deep dives, while consumer providers may use sampling or only investigate if other issues are detected. This behavior is also subject to change over time.
• Shared Resources: If any domain in the redirect chain is a shared resource (e.g., a link tracking service) and is used by senders of problematic mail, your email could inherit those negative associations, regardless of your own sending practices.

Key considerations

• Minimize Redirects: To reduce potential issues, aim to minimize the number of redirects in your email links. Every additional hop introduces another point of potential failure or scrutiny. For more on this, see Audience Point's guide on links hurting deliverability.
• Monitor Domain Reputation: Regularly monitor the sender reputation of all domains involved in your redirect chains, including your own and any third-party tracking domains. A sudden drop in reputation could indicate an issue. You can learn more about understanding your email domain reputation.
• Use Reputable Services: If using third-party link tracking or shortening services, ensure they have a strong and consistent sender reputation. Services with a history of abuse can quickly land you on blocklists (or blacklists).
• Test Deliverability: Perform thorough deliverability testing when implementing or changing redirect structures to identify any unexpected inbox placement issues before a full campaign send.
• Consider Alternatives: Explore alternative tracking methods that consolidate data collection without requiring multiple redirects, such as server-side solutions or single-hop tracking domains, as one marketer found success with Cloudflare Workers.

Key opinions

• Negative Reputation: Many marketers believe that multiple chained domains can inherently be perceived as a negative reputation signal by email filters, regardless of the speed or HTTPS use.
• Affiliate Marketing Complexity: There is a common observation that chained redirects significantly complicate email deliverability for affiliate campaigns, where multiple tracking services are often involved.
• Individual Hop Reputation: Marketers recognize that each individual hop or domain within a redirect chain carries its own distinct reputation, and a poor reputation on any of these could jeopardize delivery.
• Variability is Key: Outcomes regarding chained redirects are often seen as highly variable, depending heavily on the specific links used and the filtering practices of different providers.
• Seeking Alternatives: Some marketers are actively seeking and implementing more streamlined solutions, such as white-labeled worker scripts, to consolidate tracking and avoid redirect chains altogether.

Key considerations

• Avoid Chained Domains: It is generally recommended to avoid using multiple chained domains for link tracking in emails to prevent potential negative reputation hits. This aligns with advice on drawbacks of using redirects.
• Assess Each Hop: Before deploying, marketers should consider the reputation of each domain in their redirect chain, especially when using third-party services. Monitoring your email sending reputation is a continuous task.
• Experiment and Observe: Given the lack of definitive public documentation from ISPs, marketers may need to experiment with different link structures and closely monitor deliverability to understand the specific impact on their campaigns.
• Seek Streamlined Solutions: Prioritize solutions that reduce the number of redirects while still achieving tracking goals. White-labeling or direct API integrations can be effective alternatives.

Key opinions

• Mechanical Following: Experts confirm that MBPs (Mailbox Providers) can and do mechanically follow redirect chains. However, this is more consistently observed with enterprise filters than with consumer providers.
• Content and URL Visibility: When redirects are followed, MBPs will likely know the URLs of each step and potentially the content. If all steps are legitimate, it might not be an issue.
• Shared Resource Risk: A significant concern is the use of shared resources (domains) in the chain. If other senders abusing that shared resource are sending problematic mail, it can negatively affect your deliverability, regardless of your practices.
• Scalability Challenges for ISPs: Following redirects at scale is computationally expensive for consumer providers. They may employ sampling, track only the first hop's reputation, or only delve deeper when other message issues are present.
• Dynamic Filtering: Filtering rules related to redirects are not static; they can change frequently. What works today might not work tomorrow.

Key considerations

• Trust and Reputation Inheritance: Consider that your sender reputation can be influenced by the reputation of every domain in your redirect chain. A redirection to a suspicious domain can severely impact email reputation and deliverability.
• Transparency is Key: Ensure that all domains in your redirect chain are legitimate and not associated with malicious activity or known blacklists (or blocklists). Transparency helps in building trust with MBPs.
• Understand ISP Behavior: While large providers may follow redirects, the consistency and depth of this inspection are not guaranteed. Don't assume full inspection unless empirically verified for your specific use case. This includes URL alignment for intermediate redirect links.
• Mitigate Shared Domain Risk: If using a shared redirect service, choose one with an excellent reputation and robust abuse prevention mechanisms. Otherwise, consider dedicated domains for your redirects.
• Continuous Monitoring: Given the dynamic nature of filtering, continuous monitoring of your email campaigns and feedback loops is essential to detect any changes in deliverability performance related to redirects. More on email sender reputation.

Key findings

• Security Protocols: Official documentation from email providers and security standards bodies frequently emphasize the importance of HTTPS for all links to ensure secure transmission and prevent tampering, reducing the likelihood of links being flagged as suspicious.
• Spam & Abuse Signals: Documentation on spam filtering algorithms often mentions link obfuscation, excessive redirects, or redirects to known malicious domains as strong indicators of spam or phishing attempts. Such practices will invariably impact domain reputation.
• Sender Policy Framework (SPF): While not directly about redirects, SPF records are crucial for authenticating the sending domain. Any link tracking or redirection should maintain alignment with email authentication protocols to avoid raising red flags.
• Domain Reputation in General: Major ISPs (e.g., Google, Microsoft) publish guidelines that highlight the importance of overall domain reputation, including the reputation of linked domains. Any domain in a redirect chain can contribute to this assessment, affecting Gmail deliverability.
• User Experience Focus: Documentation often implicitly or explicitly promotes a good user experience. Long, slow, or unexpected redirect chains can degrade user experience, which ISPs may factor into their filtering decisions.

Key considerations

• HTTPS Across All Hops: Ensure that every single step in your redirect chain, from the initial click to the final destination, uses HTTPS. This is a fundamental security practice that builds trust.
• Reputable Tracking Services: If utilizing third-party services for link tracking, choose providers with established reputations for deliverability and strict anti-abuse policies. This is especially true for services that employ URL shorteners.
• Minimize Redirect Count: While not explicitly prohibited, fewer redirects are generally better from a technical and trust perspective. Simplify link paths where possible.
• Monitor Blocklists: Regularly check if any of the domains in your redirect chain, especially intermediate ones, have landed on IP or domain blocklists. Being on a blocklist can severely impact email reputation.