How do URL shorteners and domain reputation impact email deliverability?

Key findings

• Shared shorteners: Publicly available and unpoliced URL shortener hostnames, such as bit.ly, are frequently abused by spammers. This association can lead to your emails being flagged as spam or blocked, irrespective of your own sending practices.
• Domain reputation: Every domain included in an email, including those in links and images, contributes to your overall domain reputation. A poor reputation on any linked domain can negatively impact your sender score and inbox placement.
• Spam association: Data suggests a very high percentage of links from generic URL shorteners are associated with spam, indicating a significant risk for legitimate senders who use them.
• Redirect chains: Mail filters may follow redirection chains, evaluating the reputation of all intermediate steps. Long or suspicious redirect chains can be perceived as problematic, potentially leading to deliverability issues.

Key considerations

• Control your domains: Prioritise using domains you control for all links and images within your emails. This includes using branded shortener domains or custom subdomains for tracking links.
• Transparency: While URL shorteners hide the destination, mailbox providers (like Google) increasingly favour transparency. Explicit, full-length URLs are generally safer for deliverability.
• Vendor support: Choose email service providers (ESPs) that support custom domains for tracking and image hosting, rather than requiring their shared hostnames in your emails. This helps maintain your own brand’s reputation.
• Monitor deliverability: Regularly monitor your email deliverability and look closely at hostnames in your links and images if you experience content-filtering based delivery problems. For more detail, SMTP2GO's blog highlights caution when using URL shorteners.

Key opinions

• Shared shortener risk: Many marketers view generic URL shorteners as high-risk, noting their potential to damage sender reputation due to widespread abuse by spammers.
• Reputation impact: It’s widely believed that linking to low-reputation sites or using shortened links (especially unbranded ones) can directly harm email deliverability and open rates.
• Blacklisting concerns: A significant concern is that link shorteners can cause a sender’s domain to be blacklisted (or blocklisted), severely impacting email marketing campaigns and halting delivery.
• Transparency preference: There's a growing understanding that transparency and trust in email communications are paramount, leading some to suggest that explicit, full-length URLs are preferable to hidden, shortened ones.

Key considerations

• Avoiding link shorteners: Many marketers advocate for avoiding generic URL shorteners altogether to prevent deliverability issues, as highlighted by AtData's article on link shorteners hurting email deliverability.
• Custom domain usage: For tracking links and image hosting, marketers are encouraged to use custom subdomains of their primary domain (white-labeling) to maintain control over their reputation. This is directly addressed in our article on link shorteners and ESP click tracking.
• Evaluate vendor practices: It's important to select ESPs that allow for brand-aligned link management and don't force the use of their own shared, potentially problematic, hostnames.
• Focus on content and CTAs: Rather than relying on shorteners for aesthetics, focus on clear, attractive calls to action (CTAs) within the email content itself. This approach not only improves deliverability but also often leads to better click-through rates, as discussed in our article on link shorteners in email marketing.

Key opinions

• Enduring risks: The problems associated with URL shorteners remain as relevant today as they were a decade ago, if not more so, due to their continued use by malicious actors.
• Control is key: It is highly recommended to avoid linking to any hostname or domain not directly controlled by the sender, extending beyond just URL shorteners.
• High spam rates: Statistical data indicates that a vast majority of Bit.ly links are flagged as spam, making their use a significant risk to deliverability.
• Redirect chain scrutiny: Mail filters often inspect entire click chains, and the reputation of intermediate redirect steps is considered. Long redirect chains are generally viewed negatively.

Key considerations

• Custom subdomains: Serious email service providers should support custom domains (specifically subdomains of the sender's primary domain) for link tracking and image hosting. This is crucial for managing your domain reputation effectively.
• Impact of redirects: If an intermediary is used as a pure redirector, its reputation will be the dominant factor affecting deliverability, not the final destination. Understanding how link redirects affect reputation is vital.
• Content filtering: If email delivery issues appear to be content-filtering based, a detailed examination of all hostnames in links and images within your email body is warranted.
• Long-term strategy: While current mail might not face issues, the increasing importance of link reputation means it's a critical factor to consider for future email delivery success, as detailed by Word to the Wise on Bit.ly and blocking.

Key findings

• Sender reputation cornerstone: A low IP or domain reputation is frequently cited as the primary reason emails are filtered to spam, underscoring the vital role of every link’s associated domain reputation.
• Authentication importance: Not having proper authentication records, such as a DMARC record, can negatively impact your domain reputation and email deliverability, as mailbox providers may count it against you.
• Content's role: The content of your email, including links, is a significant factor in content-driven deliverability issues, influencing how your mail is perceived by filters.
• Avoiding bad links: Linking to low-reputation sites or using suspicious shortened links is explicitly identified as damaging to deliverability.

Key considerations

• Proactive reputation management: Focus on building and maintaining a strong sender reputation across your IP address and all associated domains. This involves consistent, good sending habits.
• Link to reputable sources: Always link to trustworthy and relevant sites. Avoid domains or URL shorteners known for abuse. Our guide on what happens when your domain is on a blocklist provides more context.
• Full domain control: Ensure you control all domains and subdomains used in your email content, including those for tracking and image hosting, to prevent third-party issues from affecting your deliverability. This is part of understanding your email domain reputation.
• Holistic approach: Recognise that links are part of a broader content reputation, impacting deliverability alongside other factors. Customer.io's email deliverability best practices guide highlights this comprehensive view.