Why are my Marketo emails not arriving in Gmail inboxes even with opt-ins and showing as delivered?

Key findings

• Definition of delivered: Most ESPs, including Marketo, define 'delivered' as the successful handoff of an email to the recipient's mail server. It does not guarantee the email landed in the primary inbox or any specific folder. A guide from Scribd on email marketing elaborates on this point.
• Gmail's filtering: Gmail is highly effective at delivering email and rarely drops messages entirely. If an email shows as delivered but isn't visible, it's often due to Gmail's sophisticated filtering system placing it in a different tab (like Promotions or Social) or a hidden folder.
• Recipient-side factors: Individual user settings, filters, or the use of third-party email clients can cause emails to be automatically moved or hidden, even from opt-in subscribers. Checking for these is crucial.
• Diagnostic limitations: Troubleshooting a small number of isolated missing emails can be challenging without access to detailed SMTP logs or direct input from the recipient.
• Log analysis: Accessing the full delivery log files from your ESP, which include the SMTP response codes, is essential to confirm whether the email was truly accepted by Gmail's servers (indicated by a 250 OK status).

Key considerations

• Verify recipient checks: Ensure recipients check all Gmail tabs (Primary, Social, Promotions), their spam folder, and even the trash/bin, as well as using Gmail's search function for the missing email. Our article on Gmail tabs can provide further insight.
• Conduct internal tests: Send test emails from Marketo to a newly created Gmail address to observe its delivery behavior and identify any patterns.
• Request detailed logs: Insist on obtaining detailed SMTP logs from Marketo support for the specific missing emails to confirm the exact delivery status reported by Gmail's servers.
• Check list hygiene: Confirm that the recipient addresses are not on a suppression list or marked as non-sendable within Marketo. A clean list is fundamental to improving Gmail deliverability.
• Evaluate client usage: Ask the recipient how they access their email (e.g., web interface, specific desktop client), as third-party clients can sometimes have their own filtering rules. FasterCapital highlights the use of labels and filters in Gmail.

Key opinions

• Initial investigation: The first step is always to instruct recipients to check all possible locations, including different tabs and folders within their Gmail interface.
• Client impact: Third-party email clients can sometimes interfere with how emails are displayed or organized, leading to them not appearing where expected.
• Limited data challenges: Troubleshooting when only a couple of emails are reported missing is extremely difficult, as it's hard to identify a systemic issue without more data.
• Recipient rules: It's common for individual recipients to have their own mail client rules or filters that might automatically move emails to less visible folders, including the trash or 'bin'.
• Log access: Marketers often need to engage with their ESP's support team to access granular delivery logs, as standard activity reports may lack the necessary detail (e.g., SMTP response codes) to diagnose the issue fully. See our general guide on emails not appearing in the inbox.

Key considerations

• Customer communication: Educate sales teams or customer support on how to guide recipients through checking all possible email locations in Gmail.
• Test with new accounts: Regularly send test emails to a fresh, dedicated Gmail account to monitor inbox placement behavior for your specific Marketo setup.
• Understanding 'delivered': Internal teams should understand that 'delivered' status means acceptance by the receiving server, not guaranteed inbox placement. More on this is discussed in our expert guide to email deliverability.
• Investigate suppression: If changing a recipient's email address resolves the issue, investigate whether the original address was on a suppression list, had a non-sendable status, or was accidentally bounced, rather than truly 'delivered' but hidden.

Key opinions

• Gmail's non-loss policy: Google is built to ensure emails are not simply 'dropped.' If an email shows as delivered but isn't found, it's highly probable it's been filtered elsewhere within the recipient's account rather than lost. This is consistent with our observations on why Gmail sends mail to spam folders.
• Common hiding places: The most frequent reasons for 'missing' emails are placement in Gmail's various tabs (Promotions, Social) or redirection by specific rules set up within the recipient's mail client or by the recipient themselves.
• The 'bin' folder: It's a common oversight, but emails can sometimes be accidentally routed to the 'bin' or trash folder, especially if custom rules are in place, and these might not show up in standard searches.
• Diagnostic difficulty: Attempting to troubleshoot based on only one or two anecdotal reports of missing emails is often unproductive due to the lack of sufficient data to identify a pattern or root cause. More on why emails go to spam.
• Importance of SMTP logs: Confirming a 250 OK SMTP response in the delivery logs is crucial for establishing that the email was indeed accepted by the receiving mail server, shifting the focus of troubleshooting to the recipient's side.

Key considerations

• Thorough recipient checks: Advise recipients to perform comprehensive checks, including all tabs (Primary, Social, Promotions), spam, trash, and a direct search within their Gmail account. Our guide on Gmail delivery delays offers further context.
• Replication attempts: If possible, try to replicate the issue by sending the exact same email through Marketo to your own test Gmail accounts, especially newly created ones, to see where it lands.
• Review user email access: Inquire about how the recipient accesses their Gmail (web browser, mobile app, desktop client) as external applications can apply their own filtering rules that override Gmail's default behavior.
• Data-driven diagnosis: Rely on robust data from ESP logs and Gmail Postmaster Tools rather than isolated reports. The Ultimate Guide to Google Postmaster Tools V2 provides comprehensive information on this.

Key findings

• Meaning of 'delivered': Documentation from Marketo and other ESPs typically defines 'delivered' as the successful handoff of an email to the recipient's mail server. It does not equate to the email landing in the primary inbox or being seen by the recipient.
• Gmail's tab system: Gmail's documentation explains that emails are automatically categorized into tabs like Primary, Social, and Promotions. This categorization is based on various factors, including content, sender behavior, and user engagement.
• User-defined filters: Gmail's help resources describe how users can set up custom filters and rules that automatically move or archive incoming emails, which can lead to messages being 'missing' from the main inbox.
• Engagement signals: Major ISPs, including Google, explicitly state that user engagement (e.g., opens, clicks, replies, marking as 'not spam') plays a significant role in determining future inbox placement. Lack of engagement can lead to filtering to less prominent folders or even the spam folder, as detailed in our guide on boosting email deliverability rates.
• Sender reputation: Documentation emphasizes that maintaining a strong sender reputation, built on consistent, positive sending practices, low complaint rates, and proper authentication, is paramount for optimal inbox placement. This is a key focus of our articles on Google Postmaster Tools domain reputation.

Key considerations

• Adhere to best practices: Consistently follow email marketing best practices, including explicit opt-ins, clear unsubscribe options, and relevant content, to build and maintain a positive sender reputation.
• Monitor deliverability metrics: Regularly monitor your email deliverability, not just send and open rates, but also inbox placement using tools and methods described in how to run an email deliverability test.
• Implement authentication: Ensure your domain has correctly configured SPF, DKIM, and DMARC records to establish trust with mailbox providers. Our guide on DMARC, SPF, and DKIM provides a simple overview.
• Analyze engagement trends: Pay close attention to declining open or click rates, as these can be early indicators that your emails are landing in less visible folders or being filtered more aggressively.
• Content optimization: Continually optimize your email content to reduce the likelihood of being flagged by spam filters, even when sent via a trusted IP address. This helps to avoid issues such as transactional emails going to spam at Gmail.