Why is Gmail blocking my emails despite high reputation in Google Postmaster Tools?

Key findings

• Data delay: Google Postmaster Tools data typically has a delay of up to two days. This means a recent reputation dip or blocking event might not yet be reflected.
• IP vs. domain reputation: While Postmaster Tools primarily shows domain reputation, Gmail also considers the reputation of your sending IP address. A low IP reputation can lead to blocks even if your domain looks good.
• Specific mail streams: Blocks might not affect all your mail. Transactional emails, marketing campaigns, or even specific content types could be flagged, while other streams remain unaffected.
• Authentication issues: Problems with your email authentication, such as SPF, DKIM, or DMARC, can cause emails to be blocked or sent to spam, regardless of your overall reputation. Ensure these protocols are correctly configured and aligned.

Key considerations

• Check SMTP responses: The error message from the SMTP server often provides specific reasons for the block, which can be more immediate and detailed than Postmaster Tools data.
• Review content and links: Certain content, including common link shorteners like bit.ly links, or attachments, can trigger spam filters, irrespective of your overall sender reputation.
• Sender behavior: High complaint rates, low engagement, or sudden spikes in sending volume can quickly degrade reputation in real-time, even if Postmaster Tools has not caught up yet. For more information, read about why emails go to spam.

Key opinions

• Postmaster Tools latency: Many marketers note that GPT data has a significant delay, often up to two days, making it difficult to diagnose immediate blocking issues. What you see there isn't always current.
• IP reputation matters: Even with a high domain reputation, a poor IP reputation can cause blocks, particularly if those IP addresses are being used for outgoing mails that trigger bounces.
• Targeted blocks: Blocks might not be universal across all mail streams. Marketers observe that specific campaigns or types of emails are more prone to being blocked, indicating a content or recipient engagement issue.
• Shared link issues: Some marketers have reported blocks specifically tied to the inclusion of widely used link shorteners like bit.ly links in their emails, suggesting that even seemingly benign elements can be problematic.

Key considerations

• Monitor current SMTP responses: Relying solely on Postmaster Tools can be misleading due to its delay. Real-time SMTP bounce messages provide the most accurate and immediate feedback on why emails are being blocked.
• Investigate all sending domains: Remember that your SPF and DKIM domains may differ from your main domain in GPT, and their reputations are equally crucial.
• Analyze mail streams: Determine if the blocks are occurring across all mail or only specific types of messages or campaigns. This helps pinpoint the root cause, whether it's content, audience, or volume related.

Key opinions

• Retrospective data: Experts emphasize that GPT is retrospective, meaning it shows past performance. Current blocking issues might be due to very recent activity not yet aggregated and displayed.
• rDNS and authentication alignment: The rDNS of the sending IP and the alignment between SPF/return-path domains and DKIM domains are crucial. Discrepancies here can lead to blocks, even if the primary domain reputation is good.
• Link reputation: The reputation of links included in emails, especially those from shared shorteners like bit.ly, can independently trigger blocks. If these links are associated with spam, your email may be penalized.
• Engagement signals: Gmail heavily weighs user engagement. Even with high reputation, a sudden drop in opens/clicks or a spike in spam complaints will negatively impact deliverability.
• Sales outreach impact: Unsolicited sales outreach from the same domain can quickly damage reputation, affecting even legitimate marketing emails.

Key considerations

• Temporary cessation of sending: If blocked, consider stopping sending for 2 to 4 days to allow filters to reset and reputation to stabilize. This cooling-off period can be crucial.
• Strategic re-warming: When resuming, re-warm your domain by starting with your most engaged users. Gradually increase volume as deliverability improves. This proactive reputation management helps demonstrate positive sending behavior.
• Data hygiene and segmentation: Clean your sending data by focusing on actively engaged subscribers. Removing inactive or problematic contacts can significantly boost deliverability.
• Monitor blocklists (blacklists): Even if not the direct cause, being listed on a public blocklist or blacklist can impact perception. Regularly check common blacklists and work to get delisted if necessary.

Key findings

• Authentication is fundamental: Google explicitly states that all bulk senders must authenticate their emails with SPF, DKIM, and DMARC. Failure to do so, regardless of perceived reputation, leads to rejection.
• User feedback is critical: Gmail's filters heavily rely on user signals, such as spam complaints and engagement (opens, clicks). High spam complaint rates (above 0.3%) are a major red flag.
• Postmaster Tools limitations: Documentation confirms that Postmaster Tools reports on domain reputation, not always IP reputation, and does not provide real-time data or granular reasons for individual blocks.
• Content quality: Spam triggers in email content, including suspicious links, too many images, or poor formatting, can lead to filtering, irrespective of sender reputation.

Key considerations

• Implement DMARC fully: Moving to an enforced DMARC policy (p=quarantine or p=reject) is crucial for protecting your domain from abuse and signaling legitimacy to Gmail. Consider reviewing the ultimate guide to Google Postmaster Tools V2.
• Maintain low spam rates: Gmail and Yahoo's new requirements explicitly call for a spam complaint rate below 0.3%. Anything above this threshold can trigger significant deliverability issues.
• Provide easy unsubscribe: Mandatory one-click unsubscribe links are now required for bulk senders. Making it easy for users to opt-out reduces spam complaints.