How do public URL shorteners affect email deliverability and what are the best practices for app download links in email?
Matthew Whittaker
Co-founder & CTO, Suped
Published 2 May 2025
Updated 16 Aug 2025
7 min read
When sending emails, especially marketing or transactional ones, every element, including your links, can influence whether your message lands in the inbox or the spam folder. Public URL shorteners, while convenient for social media or character-limited platforms, introduce a layer of redirection that can raise red flags with mailbox providers and spam filters. This is particularly true for app download links, where the journey from click to install is critical.
I often see questions about how a single, seemingly innocuous link could derail an entire email campaign. For instance, a client recently inquired about a peculiar, publicly shortened URL in their email that directed users to a page for selecting their phone type before taking them to the respective app store. The concern was whether this one link could cause deliverability issues. The short answer is yes, it absolutely can.
The deliverability risks of public URL shorteners
Public URL shorteners are services like Bitly or Shorter.me that allow you to condense long URLs into much shorter, more manageable ones. While they serve a practical purpose, their impact on email deliverability is often negative. Mailbox providers scrutinize email content for anything suspicious, and common public shortener domains are frequently abused by spammers and phishers. This association can tarnish the reputation of these shared domains, leading to legitimate emails being flagged or even outright blocked.
When an email contains a publicly shortened URL, the recipient's email server cannot immediately see the final destination of the link. This obfuscation is a tactic often employed by malicious actors to hide the true, potentially harmful, destination. Mailbox providers, therefore, view such links with suspicion. They might increase the spam score of your email, sending it to the junk folder, or in severe cases, your sending domain could end up on a blacklist (or blocklist).
The impact on your sender reputation is significant. While one instance might not immediately condemn your entire sending practice, consistent use of shared public shorteners can chip away at your trustworthiness. This can lead to a gradual decline in your email deliverability rates, affecting your ability to reach your subscribers' inboxes consistently.
Why public shorteners pose inherent risks
The core issue with public URL shorteners lies in the shared domain. When you use a service like Bitly, for example, your shortened link uses the bit.ly domain. This domain is shared by thousands, if not millions, of users. If even a small percentage of these users engage in spammy or malicious activities, the entire domain's reputation suffers. Mailbox providers monitor these shared domains closely and are quick to blocklist (or blacklist) them if they detect abuse.
Even if your intentions are legitimate, your emails could be caught in the crossfire simply because of the link's domain. Mailbox providers prioritize the safety of their users, and a common red flag is a link that hides its true destination. This is why many email marketers advise against using these services for email campaigns. They can lead to a decrease in domain reputation and an increased chance of your emails landing in spam.
Furthermore, many email service providers (ESPs) use their own link tracking and redirection mechanisms. When you combine a public URL shortener with an ESP's tracking, you're adding another layer of indirection. This can complicate the path to your desired destination and further obscure the true nature of the link in the eyes of spam filters.
Public URL shorteners
Shared reputation: You are tied to the sending behavior of all other users of that shortener, making your emails vulnerable to deliverability issues caused by others' spammy activity.
Increased spam filtering: Mailbox providers view these links with suspicion due to their common use in phishing and malware distribution.
Lack of branding: The shortened URL doesn't reflect your brand, which can erode trust and professionalism for recipients.
Custom branded shorteners
Controlled reputation: You maintain full control over the domain's reputation, as it's dedicated solely to your links.
Improved deliverability: Less likely to be flagged by spam filters because the domain is known and trusted by mailbox providers.
Enhanced branding and trust: URLs reflect your brand, increasing recognition and recipient confidence.
Best practices for app download links in email
When it comes to app download links in email, the goal is to get users to the correct app store as seamlessly as possible. Given the risks associated with public URL shorteners, direct linking is generally preferred. However, app download links can be lengthy and vary by operating system, making a simple direct link cumbersome or requiring a landing page that detects the user's device. To maintain good deliverability while providing a good user experience, there are several best practices.
The ideal scenario is to have a dedicated landing page on your own domain that intelligently redirects users to the correct app store based on their device. This gives you full control over the user experience and the link's reputation. For instance, if a user clicks an app download link, your landing page can detect whether they are on an Apple or Android device and redirect them to the relevant App Store or Google Play. This approach ensures a consistent and branded experience while avoiding the pitfalls of shared shortener domains.
Another option is to offer distinct buttons or links for each app store directly within the email itself, labelled clearly. This gives the user immediate control and clarity. However, this might not be suitable if space is limited or if you prefer a cleaner email design. Remember, the key is to ensure transparency in your links to avoid triggering spam filters.
Best practices for app download links
Use a dedicated landing page: Host a page on your own domain that detects the user's device (iOS/Android) and automatically redirects them to the appropriate app store.
Offer clear, distinct links: Provide separate buttons or text links for iOS and Android download pages directly in the email. This is very transparent.
Use branded custom shorteners (if necessary): If you must shorten links, use a service that allows you to brand your shortened URLs with your own domain, instead of a generic public one.
Test thoroughly: Always test your app download links on various devices and email clients to ensure they function as intended and provide a positive user experience.
Custom domains and alternative strategies
If shortening links is unavoidable, the best approach is to use a custom branded URL shortener. Many shortening services, including Bitly, offer enterprise versions where you can use your own domain for the shortened links (e.g., yourbrand.link/app). This way, the link appears legitimate and directly associated with your brand, which significantly reduces the risk of triggering spam filters. You retain control over the reputation of that specific domain.
Another alternative is to use your Google or Microsoft Postmaster Tools to monitor your domain and IP reputation. These tools provide valuable insights into how mailbox providers perceive your sending practices, including any issues related to links. Regularly checking these tools can help you identify and address potential problems before they severely impact your deliverability. For more on this, explore our guide on improving domain reputation.
Ultimately, transparency and consistency are key. Mailbox providers favor clear, consistent sending patterns from domains with good reputations. Using your own domain for links, even if they redirect, builds trust and helps ensure your emails reach the inbox. It's a fundamental step in maintaining strong email deliverability and avoiding potential blocklisting issues.
Views from the trenches
Best practices
Always use a custom branded domain for any shortened links within your emails to maintain sender reputation.
Implement a dedicated landing page on your owned domain for app downloads to intelligently redirect users.
Ensure your app download process is optimized for mobile devices, offering a seamless and intuitive experience.
Regularly monitor your domain and IP reputation through postmaster tools to preemptively address any issues.
Common pitfalls
Relying on generic public URL shorteners can lead to shared bad reputation and increased spam filtering.
Not testing app download links across various devices and email clients can result in broken experiences.
Ignoring the user experience for desktop users when designing mobile-first app download flows.
Sending emails with opaque or suspicious-looking links that raise red flags with mailbox providers.
Expert tips
Prioritize sending emails from a well-maintained domain with a strong reputation for optimal deliverability.
Consider using a subdomain specifically for tracking or redirect links to isolate any potential issues.
Ensure that any redirects are clearly visible and not cloaked, which can improve trust with both users and filters.
For app links, deep linking directly to the app stores is always preferred over multi-step redirect pages.
Marketer view
Marketer from Email Geeks says they were concerned about a public shortener being used for app download links and how it might affect deliverability, especially since the redirect wasn't visible.
2022-05-20 - Email Geeks
Expert view
Expert from Email Geeks says that to be safe, clients should use a white-label shortener service with their own domain or find a non-email way to share the link.
2022-05-20 - Email Geeks
Keeping your email links trustworthy
While public URL shorteners offer convenience, their impact on email deliverability can be detrimental due to shared reputation issues and increased scrutiny from spam filters. For critical links like app downloads, prioritizing a branded, transparent, and user-friendly experience is paramount.
Investing in a custom domain for your links, or creating a device-aware landing page on your own domain, not only enhances deliverability but also strengthens your brand's credibility. By adopting these best practices, you ensure your emails reach their intended audience, and your app download links function effectively and reliably.
Apple or 
Android device and redirect them to the relevant 
App Store or 
Google Play. This approach ensures a consistent and branded experience while avoiding the pitfalls of shared shortener domains.
Microsoft Postmaster Tools to monitor your domain and IP reputation. These tools provide valuable insights into how mailbox providers perceive your sending practices, including any issues related to links. Regularly checking these tools can help you identify and address potential problems before they severely impact your deliverability. For more on this, explore our guide on improving domain reputation.
