Do URL shorteners like Bit.ly hurt email deliverability?

Yes, public URL shorteners can negatively impact email deliverability. They are often used by spammers to mask malicious links, leading to a poor shared reputation for the shortener's domain. When you use such a shortener, your emails can inherit this bad reputation, causing them to be flagged by spam filters and potentially ending up in the spam folder or being blocklisted.

What is domain reputation and why is it important for email?

Domain reputation is a trust score assigned to your email sending domain by ISPs. It's built based on factors like sending volume, spam complaints, bounce rates, and engagement. A good domain reputation tells ISPs you are a legitimate sender, increasing the likelihood of your emails reaching the inbox.

What are the alternatives to using public URL shorteners for email?

The best alternative is to use your own branded shortener domain or custom tracking domains provided by your Email Service Provider (ESP). This involves setting up a CNAME record that points a subdomain of your primary domain to the ESP's tracking servers, keeping the link's reputation tied to your own trusted domain.

How do non-shortened external links impact email deliverability?

ISPs monitor the reputation of all domains linked in an email. If you link to a domain with a history of spam or suspicious activity, even if it's not a shortener, your email can be flagged. This is why it's critical to ensure all third-party links in your emails point to reputable destinations.

Does the length of a URL affect email deliverability?

No, the visible length of a URL in the HTML part of your email does not inherently affect deliverability. What matters most is the reputation of the domain that the URL points to, whether it's shortened or not, and whether that domain is associated with spamming activities.

How do URL shorteners and domain reputation impact email deliverability? - Sender reputation - Email deliverability - Knowledge base

Email deliverability is a complex landscape, and understanding how different elements impact your ability to reach the inbox is crucial. When crafting your email content, every component plays a role, and links are no exception. The domains you link to, particularly through URL shorteners, can significantly affect how mailbox providers view your messages and, ultimately, whether they land in the inbox or the spam folder.

At the heart of email deliverability lies sender reputation, which is heavily influenced by your domain reputation. This reputation is essentially a trust score that internet service providers (ISPs) assign to your sending domain. A good reputation signals trustworthiness, while a poor one raises red flags, leading to increased filtering or outright rejection of your emails.

While URL shorteners offer convenience and analytics, their impact on your domain reputation and deliverability can be detrimental. It's a critical area to examine, as even well-intentioned emails can suffer if the links within them carry a poor reputation.

The basics of domain reputation

Domain reputation is a dynamic score that ISPs (Internet Service Providers) like Google and Yahoo use to determine the trustworthiness of your sending domain. This score is built over time based on various factors, including your sending volume, bounce rates, spam complaint rates, and subscriber engagement. A strong domain reputation is essential for successful email marketing, as it directly influences whether your emails reach the primary inbox or are diverted to spam.

Understanding your email domain reputation is a cornerstone of good deliverability. Every link you include in your email carries its own reputation. If you link to a domain with a questionable or poor reputation, your own sending domain can be negatively impacted by association. This is why vigilance over all linked content is necessary.

Mailbox providers analyze not only the sender's reputation but also the reputation of any URLs present in the email body. This content analysis helps them identify and filter out emails that might contain malicious or unwanted links. If your email contains links to domains that have been associated with spam or phishing activities, even inadvertently, it significantly increases the likelihood of your email being flagged.

The risk of public URL shorteners

Public URL shorteners, such as Bit.ly links or TinyURL, are services anyone can use to compress long URLs into shorter, more manageable ones. While they offer benefits like link tracking and aesthetic appeal, their accessibility makes them a double-edged sword for email marketers. Spammers frequently exploit these services to cloak malicious or undesirable destination URLs, bypassing initial spam filters that might otherwise detect problematic domains.

The fundamental problem is that when you use a public URL shortener, you're essentially sharing its domain reputation. If that shortener's domain is widely used by spammers, its overall reputation will decline. Consequently, emails containing links from that shortener will inherit this poor reputation, regardless of how legitimate your own content is. I’ve seen data suggesting that over 90% of some public shortener links are flagged as spammy, which is a significant red flag for any email campaign.

ISPs (Internet Service Providers) and spam filters are constantly evolving to detect and prevent unsolicited mail. They are highly suspicious of URLs that obfuscate their final destination or belong to domains with a history of abuse. Using a generic URL shortener can trigger these filters, leading to your emails being placed in the spam folder or even blocked outright (blacklisted).

This practice has caused widespread delivery problems for legitimate senders. It’s not about the length of the URL in the HTML part of the email, as that doesn't impact deliverability. It's about the reputation of the domain hosting the shortened URL. If you find your emails consistently hitting spam traps or being rejected, inspecting the hostnames in your links and images should be a primary troubleshooting step, especially if you're using shared shortener domains.

Custom domains and tracking links

To mitigate the risks associated with public URL shorteners, the best practice is to use your own branded shortener domain or, even better, leverage custom tracking domains provided by your Email Service Provider (ESP). This approach gives you full control over the reputation of the domains your links point to.

When an ESP offers custom tracking domains, it typically involves setting up a CNAME record in your DNS (Domain Name System) that points a subdomain of your primary domain (e.g., clicks.yourdomain.com) to the ESP’s tracking servers. This ensures that when recipients click a link in your email, they see your brand's domain in the URL, not a generic shortener or the ESP's shared tracking domain.

Example CNAME Record for a Custom Tracking DomainDNS

clicks.yourdomain.com. CNAME track.esp.com.

This method ensures that your link reputation is tied directly to your own domain, which you can actively manage and protect. It's a fundamental step towards improving your email deliverability and avoiding blocklists that might affect public shorteners. Moreover, it enhances brand trust and professionalism, as recipients are more likely to click on links that clearly belong to your brand.

Strategies to protect your email reputation

Beyond simply avoiding public URL shorteners, there are several key strategies to proactively protect your email reputation and ensure your links don't hinder deliverability. Maintaining a strong sender reputation is an ongoing effort that involves careful planning and consistent monitoring.

Public URL shorteners

Share a common, often abused, domain reputation.

Increase the risk of your emails being flagged as spam.

Offer no direct control over the shortener's underlying reputation.

Can lead to blanket blocks (blocklists) if the shortener is heavily used by spammers.

Custom branded domains

Link reputation is tied solely to your brand's domain.

Reduces the likelihood of being caught in spam traps due to shared poor reputation.

Provides full control and accountability for your link's reputation.

Enhances brand consistency and recipient trust.

Proactive monitoring of your domain reputation is essential. Regularly check your sender score using tools like Google Postmaster Tools. Pay attention to any sudden drops in reputation or increases in spam complaints. These can be early indicators that something is wrong with your sending practices or the links you are including.

Best practices for link management

Use custom domains: Always use your own branded subdomains for all links, including tracking and images.
Monitor link reputation: Regularly check the reputation of all domains you link to, whether directly or through redirects.
Avoid redirect chains: Long chains of redirects can be viewed suspiciously by filters.
Maintain domain health: Implement proper email authentication (SPF, DKIM, DMARC) and send consistent, engaged content.

If you encounter deliverability issues, particularly those that appear to be content-filtering based, thoroughly examine the hostnames used in all your links and images. Any hostname that you don’t control poses a potential risk, as its reputation is influenced by all its users, not just your own practices. This shared risk can ultimately damage the delivery of your mail at various recipient ISPs, making it difficult for your messages to reach their intended audience.

Views from the trenches

Best practices

Always use a custom, branded domain for all links and image hosting in your emails, ensuring full control over their reputation and avoiding shared blacklists.

Regularly monitor your domain's reputation using tools like Google Postmaster Tools to proactively identify and address any declines in sender score or increases in spam complaints.

Educate your team and clients about the risks of public URL shorteners and the importance of using controlled domains for email links to prevent deliverability issues.

Ensure that your ESP (Email Service Provider) supports custom domains for click tracking and image hosting, and configure them properly to align with your sending domain.

Common pitfalls

Relying on generic or public URL shorteners (like Bit.ly or TinyURL), which carry shared reputations that can be negatively impacted by other users sending spam.

Ignoring the reputation of third-party domains linked in your emails, as their poor standing can reflect negatively on your own sender reputation and trigger spam filters.

Using long chains of redirects or obfuscated URLs, which are often viewed suspiciously by mailbox providers and can lead to emails being marked as spam or blocked.

Failing to implement proper email authentication (SPF, DKIM, DMARC) for your sending domains, which makes it harder for ISPs to trust your emails and the links within them.

Expert tips

Any URL with a shared hostname that isn’t policed poses a problem for deliverability, especially if commonly abused by spammers.

In modern email marketing, vendors should support custom subdomains for links, allowing senders to avoid putting third-party hostnames in their emails.

Mail filters might follow click chains through multiple redirects, evaluating the reputation of intermediate steps and potentially flagging long chains as problematic.

The length of a URL in the HTML part of an email does not directly affect deliverability; the reputation of the domain linked is what truly matters.

Expert view

Expert from Email Geeks says that nothing has changed regarding URL shorteners. Never use a URL with a publicly available and unpoliced hostname in your email, especially one that's commonly abused, as this is even truer today.

2021-04-19 - Email Geeks

Expert view

Expert from Email Geeks says that you should extend this rule beyond just URL shorteners and avoid linking to anything with a hostname or domain you don't control if possible.

2021-04-19 - Email Geeks

Conclusion

The relationship between URL shorteners, domain reputation, and email deliverability is clear: shared public shorteners pose a significant risk, while custom, branded domains offer control and enhance trust. Your email’s journey to the inbox is heavily influenced by the reputation of every domain it touches, especially those linked within the message content.

Prioritizing the health of your own domains and subdomains for all email-related links is paramount. This strategic shift not only improves deliverability but also strengthens your brand identity and protects your sender reputation from factors beyond your immediate control. By doing so, you build a more resilient email program, ensuring your messages consistently reach their intended audience.