What is an email link redirect?

An email link redirect is an intermediate URL that your email client or ESP uses to route a click before taking the recipient to the final destination. This is often done for tracking purposes or to provide a cleaner link.

Why do redirects affect email deliverability?

Redirects can affect deliverability because spam filters scrutinize them for suspicious activity, such as hiding malicious destinations or excessive chaining. Poorly managed redirects can lead to a damaged sender reputation and emails landing in spam folders.

Are ESP's built-in redirects safe?

Yes, ESPs' built-in redirects are generally considered safe as they are standard practice for click tracking and are recognized by most ISPs. However, it's always best to use a custom branded tracking domain offered by your ESP to enhance trust.

Should I use URL shorteners in emails?

It's generally advised to avoid generic URL shorteners in emails because they are frequently used by spammers and can trigger spam filters. If you must shorten links, use a custom branded shortener (e.g., yourbrand.link/... ) for better deliverability and trust.

What is an open redirect and how does it relate to email?

An open redirect is a vulnerability where a URL parameter allows an attacker to redirect users to any arbitrary external domain. In email, this can be exploited to launch phishing attacks, using a legitimate-looking domain to funnel users to malicious sites, which severely harms the legitimate domain's reputation.

How can I check if my email links are causing deliverability issues?

You can use an email deliverability tester to check how your links are perceived by spam filters. Also, regularly monitor your sender reputation metrics through tools like Google Postmaster Tools and keep an eye on your spam complaint rates. Checking if your sending domain is on any email blocklist (or blacklist) can also provide insights.

What are the deliverability drawbacks of using redirects in email links? - Sender reputation - Email deliverability - Knowledge base

Email links often involve redirects, whether for tracking clicks, masking URLs, or simply routing traffic through an Email Service Provider (ESP). While redirects can offer analytical benefits, they introduce complexities that can significantly impact your email deliverability. Understanding these nuances is crucial for ensuring your messages consistently reach the inbox.

The basics of redirects in email

When you embed a link in an email, especially through an ESP, it's rarely a direct link to the final destination. Instead, it’s typically wrapped with a tracking URL. This tracking URL acts as an intermediary, logging clicks before redirecting the recipient to the intended webpage. This process allows marketers to gather valuable data on engagement, but it adds layers between the initial click and the final destination.

There are different types of redirects, ranging from the standard tracking links used by ESPs to custom link shorteners and even open redirects. Each type carries its own set of considerations for deliverability. While ESP tracking links are generally expected by Internet Service Providers (ISPs), additional or poorly configured redirects can raise red flags.

The key concern is how ISPs and spam filters perceive these redirects. They are designed to protect users from malicious content and phishing attempts. If a link's path is obscured or leads through domains with poor reputations, it can trigger filters, leading to your emails landing in the spam folder or being blocked entirely. This is why how link redirects affect email reputation and deliverability is a significant consideration.

Deliverability risks and spam filters

One of the primary drawbacks of using redirects is the potential to trigger spam filters. ISPs like

Gmail and

Outlook are increasingly sophisticated in their detection methods. They analyze not just the visible URL but also the entire redirect chain to assess its trustworthiness. If any part of this chain is deemed suspicious, your email could be flagged as spam. This is especially true for link shorteners, which can impact email deliverability.

Multiple redirects, or 'chained redirects', add further scrutiny. Each redirect introduces another domain into the path, and each of these domains has its own reputation. If one of the intermediate domains has a poor or unknown reputation, it can negatively affect the deliverability of your email. This makes it harder for recipients to trust the link, as the final destination isn't immediately clear.

The most significant risk comes from what are known as 'open redirects'. This is a URL parameter that allows an attacker to automatically redirect users to an arbitrary domain. Essentially, if a URL parameter can be edited by an external party to change the redirect destination, it becomes a severe security vulnerability. Spammers can exploit these vulnerabilities to hide malicious links behind seemingly legitimate domains, leading to phishing attacks. This practice can quickly tank the reputation of the redirect domain.

Beware of open redirect exploits

An open redirect allows malicious actors to leverage your domain's reputation to redirect users to phishing sites or malware. If your email links contain such vulnerabilities, it significantly increases the risk of your domain being blocklisted (or blacklisted) by ISPs, severely impacting your deliverability. Always ensure your redirect mechanisms are secure and not easily manipulable.

User experience and reputation impact

Beyond spam filters, redirects can also affect the user experience and, consequently, your sender reputation. A common issue is increased load time. Each redirect adds a slight delay as the browser processes the intermediate steps. While this might seem minimal, it can add up, particularly with multiple redirects, leading to a frustrating experience for recipients and potentially lower engagement rates, as noted by Email on Acid. If a link takes too long to load, users might abandon it, negatively impacting your campaign's performance metrics.

Recipient trust is another critical factor. When recipients hover over a link and see a URL that is different from what they expect or appears to be a generic shortener (like

bit.ly), they may become suspicious. This can lead to fewer clicks, increased spam complaints, and a damaged sender reputation. Building and maintaining email domain reputation requires transparency and consistent positive interactions.

Standard ESP tracking

Most ESPs use redirects for click tracking (e.g., mailgun.com, sendgrid.net). These are generally accepted by ISPs as a standard practice for analytics. The key is to ensure these tracking domains are properly configured and, ideally, branded to match your sending domain to enhance trust.

Aggressive or custom redirects

Excessive or opaque redirects, especially those using generic URL shorteners or custom scripts, can be problematic. They may be perceived as an attempt to hide the true destination, leading to higher spam scores and potential blocklisting (or blacklisting). This is a common factor in why your emails go to spam. Additionally, if you're using a forwarding service for your sending domain, it can also affect email deliverability.

Best practices for managing redirects

While eliminating redirects entirely may not be feasible due to tracking needs, you can implement best practices to mitigate their negative impact. The goal is to minimize perceived risk and maintain transparency for both ISPs and recipients. One crucial step is to use custom branded domains for your email links. This means instead of https://esp.com/track/..., your links would appear as https://links.yourdomain.com/.... This branding builds trust because recipients see your familiar domain, reducing suspicion and improving click-through rates.

You should also avoid unnecessary layers of redirects. If your ESP already uses a tracking redirect, adding another one (e.g., via a third-party URL shortener like tinyurl.com) can create a longer, more suspicious redirect chain. Remember that multiple or long links can affect email deliverability negatively. Furthermore, regularly monitor your sender reputation and check if your domains or IPs are on any email blocklist (or blacklist). This proactive approach can help you identify and address issues before they significantly impact your campaigns.

Redirect type	Deliverability impact	Best practice
ESP tracking redirect	Generally low risk, expected by ISPs for analytics.	Use custom branded tracking domains provided by your ESP. Example: SendGrid
Generic URL shortener	High risk. Often associated with spam, can trigger filters and reduce trust.	Avoid generic shorteners like bit.ly or tinyurl.com. Custom domain shorteners are better. Read more on why Bitly links can be bad for deliverability
Open redirect	Extremely high risk. Exploited by attackers for phishing, leading to domain reputation collapse and blacklisting. Trustwave	Ensure all redirects are secure and cannot be manipulated by external parties.

For ESPs that allow it, setting up a custom tracking domain is often as simple as adding a CNAME record to your DNS. This record points a subdomain (e.g., links.yourdomain.com) to your ESP's tracking server. This keeps the redirect consistent with your brand and avoids the perception of a third-party intrusion, thus improving your chances of inbox placement. The specific steps vary by provider, but the concept is consistent.

Views from the trenches

Best practices

Use a dedicated, branded subdomain for your click-tracking links to maintain sender reputation and brand consistency.

Ensure your ESP provides robust and secure tracking mechanisms to prevent open redirect vulnerabilities.

Regularly audit your email links to confirm they are resolving correctly and not leading to unexpected redirects or errors.

Educate your team on the risks of generic URL shorteners and prioritize branded, internal link management.

Monitor your domain reputation metrics closely to detect any negative impact caused by redirect practices.

Common pitfalls

Relying on generic third-party URL shorteners which are often associated with spam and can trigger strict spam filters.

Creating multiple, unnecessary layers of redirects, which can increase load times and raise suspicion with ISPs.

Using dynamically editable redirect URLs that are susceptible to open redirect attacks, damaging your domain's trust.

Failing to brand email tracking links, making them appear generic and less trustworthy to recipients and spam checkers.

Not regularly checking the reputation of your redirect domains, which can lead to unexpected blocklisting (or blacklisting).

Expert tips

A custom tracking domain is a must-have for serious email marketers, as it gives you full control and helps isolate your sending reputation from shared ESP domains.

Always test your email links across various email clients and ISPs to ensure they resolve correctly and quickly, even with redirects.

Consider the final destination of your link. If it's a known malicious site, even a trusted redirect won't save you from blocklisting (or blacklisting).

Implement DMARC policies at quarantine or reject to protect your domain from unauthorized use, including phishing via redirect exploits.

Leverage tools that allow you to preview the full redirect chain before sending an email, giving you visibility into potential issues.

Expert view

Expert from Email Geeks says: Your ESP already uses redirects for tracking. Any additional redirects add layers that spam checkers might view as an attempt to hide the real destination, potentially preventing delivery.

2022-02-07 - Email Geeks

Expert view

Expert from Email Geeks says: Link shorteners like Bitly are often viewed with more suspicion by rigid and strict email policies because of their common use in spam and phishing campaigns.

2022-02-07 - Email Geeks

Final thoughts on link redirects

While redirects are an inevitable part of modern email marketing, especially for tracking, their implementation requires careful consideration. Prioritizing transparency, using branded domains, and avoiding unnecessary layers or vulnerable open redirects are key to mitigating deliverability drawbacks. Proactive monitoring of your sender reputation and quick action on any blocklist (or blacklist) notifications will further safeguard your email program.