What causes the 'error message' when accessing links in emails and how can it be resolved?
Michael Ko
Co-founder & CEO, Suped
Published 6 May 2025
Updated 17 Aug 2025
6 min read
There's nothing quite as frustrating as crafting a perfect email campaign, hitting send, and then hearing from recipients that the links in your emails lead to an error message. It's a common, perplexing issue that often leaves both senders and recipients scratching their heads, especially when the email itself landed safely in the inbox.
These errors, ranging from "This site can't be reached" to "Access Denied" or "404 Not Found", typically indicate that while the email was delivered successfully, something prevented the recipient's device or network from accessing the linked web content. It points to a broader web connectivity or security issue rather than a direct email deliverability problem.
Understanding what causes these 'error messages' when accessing links in emails and how they can be resolved is crucial for both email marketers and IT professionals. This guide will explore the common culprits and provide actionable steps to diagnose and fix these frustrating link access issues, ensuring your valuable content reaches its intended audience.
Common causes of email link errors
Recipient-side and network restrictions
One of the most frequent causes of link access errors originates from the recipient's device or network. This can include browser extensions, such as ad blockers or privacy tools, which might erroneously interpret legitimate links as malicious and block them. Similarly, antivirus software or local firewalls can sometimes interfere, preventing the browser from reaching the linked URL. Often, these issues can lead to error messages like those seen when troubleshooting Microsoft Outlook hyperlinks.
Beyond individual devices, network-level blocks are a significant factor. Corporate networks, public Wi-Fi providers, or even Virtual Private Networks (VPNs) often implement stringent security policies. These policies can filter or block access to certain domains or IP addresses perceived as risky, causing generic links leading to error pages. This is particularly common if the network's IP address (or the IP of a VPN server) has a poor web reputation and is flagged by web application firewalls, such as those used by Cloudflare.
Cloudflare blocking access
An error message indicating that you cannot access a link, often with phrases like "Oops, something went wrong" or "Access Denied" and mentioning Cloudflare, suggests that Cloudflare is blocking access from the recipient's IP address. This is typically a security measure aimed at IPs suspected of malicious activity. Crucially, this is about the recipient's IP reputation for web access, not the sender's email IP reputation.
Sender-side link issues and infrastructure
Issues can also stem from the sender's email setup or the linked content itself. This includes basic errors like malformed URLs, where the http:// or https:// prefix is missing, or simply broken links on the destination website. If the page was moved, deleted, or never existed, a 404 "not found" error will occur, regardless of email delivery.
Email Service Providers (ESPs) commonly wrap original links for click tracking, allowing senders to gather valuable engagement data. However, problems can arise during this wrapping process or with the ESP's tracking domain configuration, leading to faulty redirects or error pages. For instance, some users encounter broken links when using SendGrid links are broken. Additionally, security filters can sometimes modify or break links, preventing proper access to your content.
Diagnosing link access problems
Troubleshooting from the recipient's perspective
The first step in diagnosing a link access problem is for the recipient to try isolating the issue. This involves attempting to access the link on various devices, such as a phone versus a laptop, and across different networks, like home Wi-Fi compared to mobile data. If the link functions correctly on one network or device but fails on another, it strongly suggests a network-specific or device-specific security configuration is at play.
Recipients should also try basic browser troubleshooting. Clearing browser cache and cookies, or trying a different web browser, can often resolve conflicts. Temporarily disabling browser extensions or plugins, particularly ad blockers or privacy tools, is also a crucial step, as these are common culprits that block content or redirects. In some cases, the fix can be as simple as ensuring a valid default web browser is correctly set in the operating system.
Recipient steps
Device/network check: Access the link on multiple devices and networks.
Browser hygiene: Clear cache, cookies, and disable extensions.
Security software: Temporarily disable VPN, antivirus, or firewall.
Default browser: Ensure a valid default web browser is set.
Sender checks
URL validation: Verify link format and destination URL.
ESP configuration: Check click tracking and link branding settings.
Server status: Confirm the linked content's server is up and running.
Domain reputation: Monitor the reputation of your linked domains.
Addressing sender-side factors and prevention
Ensuring link integrity and domain reputation
From the sender's perspective, ensuring that all links are correctly formatted and functional is paramount. Always include the full protocol, such as https://, in your URLs. Even a minor error in the link structure can lead to a site can't be reached or a 404 "not found" error when recipients attempt to click through.
Regularly monitoring the web reputation of your linked domains is also vital. This refers to the domain that hosts the content your email links point to, which might be different from your email sending domain. If this domain is perceived as suspicious by web security services, it can result in access blocks by web application firewalls or other security solutions, even if your email sending domain maintains a pristine reputation. Being listed on a web blocklist (or blacklist) can directly contribute to these access errors. You can find more information about this in our guide to email blocklists, even though this is about web blocklists.
While email delivery might succeed, some recipient security systems might still block access to the linked content if the linked domain (or the IP address of the server hosting the content) has a poor reputation or is associated with phishing. This is a nuanced distinction from what happens when your domain is on an email blacklist but can still prevent recipients from reaching your valuable content. For issues specifically related to click tracking, our guide on why tracking links might not work in Chrome can provide further insights.
Error Code
Meaning
Common Cause
Recommended Action
400 Bad Request
The server cannot process the request due to malformed syntax.
Often due to corrupt browser cache or invalid URL formatting.
Clear browser cache, check URL for errors.
403 Forbidden
Access to the resource is denied.
Server permissions, IP blocklists, or VPN/proxy blocking access.
Check server permissions, try disabling VPN, contact IT if corporate network.
404 Not Found
The requested resource could not be found.
Broken link, mistyped URL, or deleted page.
Verify URL, check if page exists, update link.
500 Internal Server Error
A generic error from the server indicating an unexpected condition.
Server misconfiguration or temporary server issue.
Contact website administrator, wait and retry.
Views from the trenches
Best practices
Regularly test your email links across different email clients and devices.
Use full HTTPS protocols for all links in your emails to ensure security and proper rendering.
Implement robust click tracking through a reputable Email Service Provider (ESP).
Ensure your website's server is stable and linked pages are not frequently moving or being deleted.
Common pitfalls
Overlooking recipient-side network restrictions, like corporate firewalls or VPNs, as a cause.
Not validating all links before sending large email campaigns to prevent broken URLs.
Assuming link errors are always an email deliverability issue when they might be web access problems.
Forgetting to check if the linked content's server is actively running and accessible.
Expert tips
Educate your recipients on basic troubleshooting steps, such as checking their VPN or browser extensions.
Maintain a clear understanding of your ESP's link tracking and branding configurations to avoid issues.
Regularly review your domain's web reputation independently of your email sending reputation.
Collaborate with your IT department for network-related access issues affecting recipients.
Expert view
Expert from Email Geeks says: An error message often indicates that Cloudflare is blocking access from an IP address suspected of malicious activity. This is usually a security issue on the recipient's side, not related to email deliverability.
2024-07-18 - Email Geeks
Marketer view
Marketer from Email Geeks says: If a senior leader is getting a link error on a company phone, it might be related to corporate network settings or a company VPN, even if they are not on the corporate Wi-Fi.
2024-07-18 - Email Geeks
Resolving email link access issues
Troubleshooting email link errors requires a comprehensive approach, examining factors from both the sender's email setup and the recipient's local environment. By systematically addressing potential causes, from basic browser hygiene and network restrictions to proper link formatting and web domain reputation, you can significantly reduce the occurrence of these frustrating messages. Effective communication between senders and recipients, and involving IT departments when necessary, is key to resolving these issues and ensuring a seamless experience for all.
Cloudflare, suggests that Cloudflare is blocking access from the recipient's IP address. This is typically a security measure aimed at IPs suspected of malicious activity. Crucially, this is about the recipient's IP reputation for web access, not the sender's email IP reputation.
