Why is Barracuda automatically unsubscribing users and how can I prevent it?

Key findings

• Automated link clicks: Barracuda security solutions routinely follow all links in incoming messages to scan for malicious content or other threats.
• One-click unsubscribe impact: If your unsubscribe mechanism allows a single click to opt out a user without a confirmation step, Barracuda's automated click will trigger a genuine unsubscribe.
• Reputation signal: An increase in Barracuda-initiated unsubscribes can indicate an escalation in their scrutiny of your email, possibly due to evolving sender reputation or perceived issues with your mail practices.
• List-Unsubscribe header: The List-Unsubscribe-Post: List-Unsubscribe=One-Click header (RFC 8058) is designed to handle one-click unsubscribes via a POST request, which can help differentiate automated clicks from human intent, though its implementation can be complex.

Key considerations

• Implement two-step unsubscribes: Require users to confirm their unsubscribe request on a landing page after clicking the unsubscribe link in the email body. This is a crucial step to prevent automated unsubscriptions.
• Review email content: If your emails contain third-party ads or suspicious content, Barracuda might increase its scrutiny, impacting your deliverability and potentially leading to more automated actions. Ensure your content adheres to best practices, as outlined in guides like Why your emails are going to spam.
• Monitor sender reputation: Proactively monitor your sender reputation to detect any negative trends that might trigger increased filtering by security gateways. You can learn more about this in our article How to improve domain reputation using Google Postmaster Tools.
• RFC 8058 implementation: Consider implementing RFC 8058 for the List-Unsubscribe header, which aims to provide a more robust one-click unsubscribe mechanism that can distinguish between human and bot interactions. Refer to the official RFC 8058 documentation for technical details.

Key opinions

• Sudden unsubscribe spikes: Marketers observe unusually high unsubscribe numbers overnight, with a common pattern linking these to Barracuda IP addresses.
• One-click vulnerability: If an unsubscribe link directly triggers a confirmation message like "Your subscription has been successfully adjusted" without an additional click, it's susceptible to automated bot actions.
• ESP limitations: Marketers often need to check if their Email Service Provider (ESP), like Ongage, supports the necessary technical implementations to prevent automated unsubscribes.
• Reputation concerns: Concerns arise that increased Barracuda scrutiny may be linked to sender practices, such as failing to remove non-openers, which could trigger more aggressive filtering behavior.

Key considerations

• Confirm unsubscribe processes: Ensure your unsubscribe links in the email body lead to a landing page requiring a second confirmation click from the user to prevent unintended opt-outs from automated systems. This is distinct from the List-Unsubscribe header.
• Implement RFC 8058: For the List-Unsubscribe header, explore implementing RFC 8058 to ensure that unsubscribe requests initiated via mail clients are triggered by a POST request, not a simple GET, helping to filter out bot clicks. Review resources such as Twilio SendGrid's deliverability guide for best practices.
• Auditing ESP capabilities: Regularly check with your ESP whether they support advanced unsubscribe header implementations and how to configure them effectively.
• List hygiene practices: Proactively clean your lists by removing inactive subscribers, especially non-openers after a set period (e.g., 60-90 days), to maintain a healthy sender reputation and avoid triggering heightened scrutiny from security gateways. This aligns with preventing issues like bot sign-ups.

Key opinions

• Decade-long behavior: Barracuda's practice of following all links in messages has been observed for at least a decade, making it a known challenge for email senders.
• Reputation escalation: An increase in Barracuda's link-clicking behavior against specific mail streams signals an escalation, implying that something in the mail stream is prompting deeper inspection, even if it's not directly engagement metrics.
• RFC 8058 intent: RFC 8058 aims to allow senders to distinguish between human and machine-initiated unsubscribe clicks by requiring a specific POST request with a 'magic cookie' for automatic opt-outs from headers.
• Hybrid unsubscribe approach: A combination of RFC 8058 for the List-Unsubscribe header and a two-step confirmation for the in-body unsubscribe link is often recommended as the most robust solution.
• Third-party content risk: Including third-party ads can cause senders to inherit the reputation of those third parties, potentially triggering more aggressive filtering from security gateways like Barracuda.

Key considerations

• Prioritize user-visible unsubscribe: Regardless of header implementation, the primary fix is to ensure the user-visible unsubscribe link in the email body requires a confirmation click on the landing page, preventing automated unsubscribes.
• Strategic RFC 8058 implementation: While beneficial, implementing RFC 8058 might not be a high priority if existing code is stable, unless already undertaking significant development. The critical aspect is checking the POST request body for the required 'cookie' (a unique identifier, also known as a magic cookie) to confirm human intent.
• Holistic deliverability review: Treat Barracuda's behavior as an early warning sign. Conduct a comprehensive review of email practices, content, and list hygiene, as detailed in our guide on email deliverability issues, to prevent broader deliverability problems.
• Authentication standards: Ensure proper email authentication (SPF, DKIM, DMARC) is in place, as robust authentication can improve trust with security gateways and potentially reduce scrutiny. Learn more in A simple guide to DMARC, SPF, and DKIM.

Key findings

• Spam action configuration: Barracuda Email Security Gateway can be configured to take specific actions when it identifies messages as spam or in violation of its policies, including potentially following links.
• New user quarantine state: Barracuda allows administrators to disable automatic account creation for new users by setting their quarantine state to 'Off', which could indirectly affect how new emails are processed and links are handled.
• Email Gateway Defense: Barracuda Email Gateway Defense assigns a spam score to messages, and based on this score, blocks messages that appear to be spam, which may involve deeper content inspection like link following.
• SPAM Act compliance: Barracuda's blog notes that email platforms verify subscribers and automatically insert unsubscribe links to comply with regulations, implying automated checks on these links.

Key considerations

• Understanding Barracuda's actions: Review Barracuda's official documentation, such as their guide on understanding key concepts, to gain insight into how their security gateway processes and filters emails, including their link-scanning mechanisms.
• Configure quarantine settings: Administrators using Barracuda products should be aware of settings like 'New User Quarantine State' to manage how new email accounts are handled, which might influence automated behaviors, as described in their guide on creating and managing accounts.
• RFC 8058 adherence: Implement the List-Unsubscribe-Post header according to RFC 8058, ensuring that any automated unsubscribe via the header requires a POST request with specific content to avoid unintended opt-outs. This distinguishes human interaction from bot activity.
• Email authentication: Maintain strong email authentication (SPF, DKIM, DMARC) to improve email trust and reduce the likelihood of messages being flagged for aggressive scanning, which could include link-following. Our deliverability tester can help verify your setup.