Why are some email subscribers receiving blank emails and how can I fix it?

Key findings

• Rendering vs. missing content: Many 'blank' emails are not actually empty but are failing to render due to issues with the email client or webmail interface.
• ISP filtering: Internet Service Providers (ISPs), like Shaw.ca mentioned in discussions, may aggressively filter or strip certain content, leading to a blank display, sometimes even without a clear bounce message.
• HTML/CSS issues: Complex or non-standard HTML and CSS can confuse email clients, causing them to fail at rendering the email body, resulting in a blank appearance.
• Diagnostic limitations: Simply forwarding an email does not reliably provide the original message's source, making it difficult to diagnose if content was truly missing or just not rendered.
• Security implications: Some blank emails can be a sign of dangerous spam or part of a preliminary attack strategy to gauge recipient susceptibility, as highlighted by Directive Blogs.

Key considerations

• Verify raw source: Always aim to view the original email's raw source or have it forwarded as an attachment to confirm if the content is truly absent.
• Inbox placement tests: Utilize inbox placement testing tools to replicate the issue across various ISPs and email clients, including specific domains like Shaw.ca.
• Content best practices: Ensure your email HTML and CSS are clean, validated, and adhere to widely accepted standards to minimize rendering problems. Avoid overly complex or non-standard coding that might trip filters.
• Email client investigation: Pinpoint which email clients or webmail interfaces (e.g., Outlook webmail) are showing the blank emails, as the fix might be client-specific.
• Proactive monitoring: Regularly monitor your email deliverability and engagement metrics to detect drops or issues early.

Key opinions

• Rendering, not missing: A common belief is that emails are not truly blank, but rather their content is being blocked or misinterpreted by the recipient's mail application, preventing it from rendering.
• CSS/HTML sanitization: Specific HTML or CSS elements might trigger sanitization routines in certain email clients or webmail providers, leading to a failure in displaying the email body.
• ISP specific quirks: Some ISPs, like Shaw.ca, may have unique or aggressive content filtering mechanisms that result in blank emails for their subscribers.
• Forwarding limitations: Marketers note that simply forwarding a blank email does not provide a reliable raw source, as the email client recreates the message.
• Client variability: The problem of blank emails can be isolated to specific mail clients (e.g., Thunderbird, Apple Mail) or webmail interfaces (e.g., Shaw webmail) rather than being universal.

Key considerations

• Original source verification: It is critical to obtain the raw source of the original email (e.g., via forwarding as an attachment) to confirm if the content was sent or stripped.
• Content validation: Marketers should regularly validate their email HTML and CSS to ensure it renders consistently across diverse email clients and webmail environments. This can prevent issues that cause marketing emails from being blocked.
• Inbox placement testing: Conducting thorough inbox placement tests (especially with seeds from problematic domains like Shaw.ca) can help replicate and diagnose blank email issues.
• ISP communication: Where possible, try to establish contact with the ISP's postmaster team to understand their filtering policies or report specific issues.

Key opinions

• Raw source verification: Experts consistently advise examining the original raw source of the email to confirm if the content was present upon initial delivery.
• Forwarding unreliability: Simply forwarding an email is not a valid test for source content, as the email client processes and recreates the message, potentially altering or omitting original data.
• Client-side rendering issues: Many 'blank' instances are due to how the email application or webmail client sanitizes or renders HTML/CSS, not because the content was missing from the server.
• ISP-specific filtering: Some ISPs may employ specific or unusual content filtering rules that could strip email bodies or make them appear empty, particularly if reputation is poor or specific elements trigger filters.
• Account access importance: Gaining direct access to a problematic email account (e.g., a Shaw.ca account) can be the most effective way to diagnose the issue firsthand.

Key considerations

• Deep dive into headers: Examine email headers meticulously for clues on how the message was processed, including authentication (SPF, DKIM, DMARC) results. A simple guide to DMARC, SPF, and DKIM can help.
• Inbox placement testing: Implement comprehensive inbox placement testing with seed lists that include the affected domains (e.g., Shaw.ca) to pinpoint rendering failures. This is a crucial step in monitoring potential blocklist impacts as well.
• Browser developer tools: When diagnosing issues in webmail, utilize browser developer tools to inspect the rendered HTML and CSS, identifying any elements that might be causing content suppression.
• ISP communication attempt: While challenging, direct communication with the problematic ISP (if an abuse desk or postmaster contact is available) can sometimes lead to insights or a resolution.

Key findings

• Anti-spam/anti-virus interference: Blank emails can be leftovers from anti-spam or anti-virus filters that actively remove content between the mail server and the client.
• Rendering logic issues: Certain CSS or HTML structures can 'trip' the sanitization or rendering logic in email applications or webmail, causing the email to fail to render visually, even if the content is technically present.
• Server-side errors: Server upgrades or unexpected system behavior can sometimes lead to email alerts or content being sent as entirely blank messages, as observed in community discussions.
• Indicator of malicious activity: Blank emails can be used by attackers to test recipient engagement, acting as a reconnaissance step before deploying more specific, harmful attacks. This risk is noted by Directive Blogs.

Key considerations

• Content validation: Developers should ensure email content conforms to established HTML and CSS best practices for email, avoiding elements known to cause rendering issues or trigger spam filters.
• Filter interaction: Understanding how anti-spam filters interact with email content is crucial. For instance, sometimes these filters remove malicious attachments, leaving a blank body.
• Server-side diagnostics: If a problem occurs after server changes, IT teams should examine server logs and configurations for any unintended content stripping or message generation errors. This is relevant for ensuring compliance with new sender requirements.
• Reputation impacts: A low sender reputation can cause ISPs to apply stricter filtering, which might include content removal. Learning what happens when your domain is blocklisted is important.