How to determine if marketing emails are going to spam?

Key findings

• Engagement metrics: A sudden or consistent drop in open rates and click-through rates often signals that emails are landing in spam or promotions tabs, rather than the primary inbox. It's a key indicator (a canary in the coal mine) that issues may be present.
• Sender reputation: Your domain and IP reputation heavily influence inbox placement. Poor reputation, often tracked via tools like Google Postmaster Tools, can lead to widespread spam filtering.
• Authentication: Proper implementation of email authentication protocols like SPF, DKIM, and DMARC is fundamental. A failure in these can cause emails to be flagged as suspicious, often landing in spam.
• Seed testing: Sending emails to a diverse set of seed addresses provides an empirical measure of where your emails are landing across various mailbox providers (MBPs).
• Complaint rates: High complaint rates (when recipients mark your email as spam) are a strong negative signal to MBPs, significantly impacting your sender reputation and increasing the likelihood of future spam folder placement.

Key considerations

• Holistic view: Relying on a single metric like open rates is insufficient. A comprehensive approach involves analyzing engagement, sender reputation, authentication, and using diagnostic tools.
• Audience segmentation: Continuously segmenting your list and suppressing unengaged contacts is crucial for maintaining a healthy sender reputation and avoiding spam folders.
• Content quality: Spam trigger words, broken links, or overly promotional content can increase the likelihood of emails being flagged by spam filters, even with good sender reputation.
• Bounce management: Regularly cleaning your list of hard bounces and managing soft bounces indicates good list hygiene, which positively impacts deliverability.

Key opinions

• Panel data effectiveness: Some marketers believe panel data is not a 1:1 match for their specific list, thus questioning its accuracy for their database, even if it comes from real recipients.
• Seed testing utility: The value of seed testing is sometimes debated, as seed list recipients may not perfectly reflect the pre-existing bias of actual subscribers, yet it serves to simulate first-time recipient behavior.
• Open rate reliability: Marketers frequently use open rates as a primary indicator, acknowledging its flaws (e.g., image blocking, anti-spam filters triggering), but finding it the most accessible metric reflecting actual audience engagement from their database.
• Engagement as core: Many marketers emphasize that consistent engagement, rather than just send volume, is key to avoiding spam folders. Low engagement can lead to filters redirecting emails.
• Subscriber permission: Obtaining express permission from recipients is repeatedly highlighted as a fundamental practice to prevent emails from being marked as spam.

Key considerations

• Consistent sending: Maintaining a regular sending schedule helps build a positive sending reputation. Inconsistent or random sending patterns can increase the likelihood of landing in spam.
• Content optimization: Careful attention to subject lines and avoiding spam-triggering keywords is important, as these elements are crucial in how spam filters classify emails.
• List hygiene: Regularly cleaning email lists, including removing unengaged subscribers or those leading to spam traps, is a critical step for improving deliverability.
• Feedback loops: Monitoring spam complaints through feedback loops (where available) allows marketers to promptly identify and address issues, helping to prevent further deliverability problems.

Key opinions

• Panel data accuracy: Experts confirm that panel data, when sourced correctly (e.g., from Return Path or eDataSource), comes from live users who received the email campaign. Dismissing it as not a 1:1 match for recipients on a list, is a misconception.
• Seed testing purpose: Seed testing is primarily designed to simulate how emails perform for new recipients with no prior engagement history, not necessarily to match an existing list precisely.
• Open rate limitations: Open rates are problematic metrics because they don't trigger when images are off, can be triggered by anti-spam filters or image caching services, and sometimes by mail clients just viewing the email list.
• Verifying issues: While low open rates can indicate a problem, they don't confirm spam filtering. Independent verification through seed testing services and panel data, which empirically measure inbox placement, is necessary to determine the root cause of deliverability issues.
• Value of free tools: Important free tools like Google Postmaster Tools and Microsoft SNDS are crucial for B2C senders to monitor domain and IP reputation, which directly affects inbox placement.

Key considerations

• Empirical measurement: For accurate diagnosis, senders should prioritize tools that empirically measure whether emails are inboxing. This removes the need for inferring deliverability solely from engagement metrics.
• IP and domain reputation: A primary cause of inbox placement issues is often poor IP or domain reputation, including being on a blacklist or blocklist. These factors must be actively monitored and addressed.
• Unengaged recipients: While not the only factor, sending to unengaged recipients significantly contributes to a declining sender reputation, leading to spam filtering. Proactive list cleaning is essential.
• Transparency in reporting: An article or tool should transparently outline the strengths and weaknesses of all available methods for assessing deliverability, rather than downplaying third-party tools that might reveal underlying IP or domain issues.

Key findings

• Sender reputation scores: Major Mailbox Providers (MBPs) like Gmail and Outlook publicly state that their filtering decisions are heavily influenced by the sender's reputation, which is calculated based on factors like spam complaints, bounce rates, and engagement.
• Authentication standards: Documentation (e.g., RFCs, Google and Yahoo sender guidelines) emphasizes the necessity of strong email authentication (SPF, DKIM, DMARC) to verify sender identity and prevent spoofing, which directly impacts trust and deliverability.
• User engagement signals: ISPs (Internet Service Providers) actively track positive engagement (opens, clicks, replies, adding to contacts) and negative engagement (spam complaints, deletions without opening) to determine future inbox placement. Documentation often highlights these metrics as crucial.
• Content quality: While less explicit on specific 'spam words,' documentation generally advises against deceptive subject lines, excessive capitalization, and irrelevant content, as these can trigger spam filters based on content analysis.

Key considerations

• Adherence to guidelines: Consistently following postmaster guidelines from major providers (e.g., Gmail, Outlook, Yahoo) is paramount. These guidelines provide explicit instructions on expected sender behavior to ensure optimal deliverability.
• Monitoring Postmaster tools: Leveraging free tools like Google Postmaster Tools and Microsoft's Sender Score / Smart Network Data Services (SNDS) provides direct data on your sender reputation and spam rates as seen by these MBPs.
• List acquisition practices: Documentation often stresses the importance of opt-in consent. Sending to non-consented lists can lead to spam trap hits and significantly damage sender reputation.
• Regular DMARC reporting: Analyzing DMARC reports, as outlined in DMARC RFCs and best practices, allows senders to gain visibility into email authentication failures and potential abuse of their domain.