What steps should I take when Gmail blocks my new IP address on SFMC?

Key findings

• Specific error message: 5.7.1 (delivery not authorized) indicates Gmail perceives the message as likely unsolicited, often pointing to content or sender reputation concerns rather than basic IP or authentication issues.
• IP warming sensitivity: Gmail is particularly cautious with mail from new IP addresses, and temporary blocks during the initial warming phase are not uncommon, even with proper setup.
• Content and audience focus: Despite a new IP, the block often suggests that Gmail's algorithms are flagging aspects of the email content or the recipient audience (e.g., perceived engagement) as potentially spammy.
• Authentication baseline: Even though your SPF/DKIM is set correctly, ensuring full DMARC compliance and proper Salesforce Marketing Cloud (SFMC) Sender Authentication Package (SAP) implementation is critical for building trust with inbox providers.

Key considerations

• Obtain detailed bounce messages: Always request or retrieve the full raw SMTP rejection message. Generic explanations can be misleading; the specific bounce code and accompanying text provide crucial diagnostic clues.
• Monitor with Google Postmaster Tools: Sign up for and regularly check your domain and IP reputation in Google Postmaster Tools. This provides direct insight into how Gmail perceives your sending practices.
• Adjust IP warming volume: If blocks occur, reduce your sending volume. Temporarily pausing or significantly decreasing sends and then slowly re-increasing can help rebuild trust. More information can be found on Salesforce Ben's IP warming guide.
• Refine audience targeting: Ensure that during warming, and especially after a block, you are sending only to your most engaged subscribers (e.g., recent clickers or openers) to generate positive engagement signals.
• Review content and list hygiene: Thoroughly review your email content for anything that might trigger spam filters. Also, ensure your lists are clean, free of unknown users or spam traps, and that all unsubscribe requests are honored.

Key opinions

• Content flags reputation: Marketers frequently note that a block message indicating "likely unsolicited mail" or "bad content" is a strong signal of a reputation problem, even if the content seems benign.
• Warming sensitivity: New IPs can be subject to heightened scrutiny by Gmail, leading to temporary blocks even during a well-executed warming plan.
• Targeting engaged users: Many marketers advise starting IP warming sends to the most engaged segments of your audience, such as recent clickers, to build positive signals quickly.
• SAP domain importance: Some users report better deliverability when sending directly from their SFMC Sender Authentication Package (SAP) domain, even if other private domains have proper authentication, suggesting domain reputation can be a factor.

Key considerations

• Detailed bounce analysis: It's crucial to get detailed SMTP rejection messages or check SFMC's _Bounce dataview to understand the precise reason for the block.
• Persistent effort: Sometimes, temporary blocks resolve simply by consistently adhering to good sending practices and slightly reducing volume, indicating that Gmail may be overly cautious with new IPs.
• Technical consistency: Ensure all sending domains (SAP and private) have perfectly aligned SPF, DKIM, and DMARC records to avoid confusing mailbox providers about your sender identity.
• Data quality scrutiny: Beyond perceived good intent, deeply inspect your segmentation and data for any errors that might lead to sending to unengaged or inappropriate recipients, as this can trigger Gmail's filters. You can also explore our guide on recovering from Gmail blocks.

Key opinions

• Error message value: The "likely unsolicited mail" message is highly diagnostic, often indicating a reputation issue that requires more than just waiting out an IP warming phase.
• Technical foundation first: Before addressing content or volume, experts stress the importance of verifying that SFMC's Sender Authentication Package (SAP) is fully implemented, including custom return-path domains matching from addresses, and that DKIM signatures are consistently passing.
• Domain reputation matters: Differences in deliverability between SAP and other private domains, even with authentication, are likely due to varying domain reputations, not an inherent SFMC flaw.
• Data and segmentation review: If technicals are solid, the next step is a deep dive into data quality, looking for segmentation errors, purchased lists, or issues with respecting unsubscribes that could generate negative signals.

Key considerations

• Utilize bounce data: Leverage SFMC's _Bounce dataview or request raw SMTP rejection messages from support for the most accurate diagnostic information.
• Monitor with Google Postmaster Tools: Regularly check your domain's and IP's health within Google Postmaster Tools to understand Gmail's specific perspective on your sender reputation.
• Address technical checks: Systematically walk through all technical checks related to modern Gmail sender requirements. Our guide on Gmail deliverability issues for new IP addresses provides additional tips.
• Sender form outreach: After exhausting internal diagnostics, submitting a detailed request via Google's sender contact form can be a necessary step.

Key findings

• Authentication mandate: Google's 2024 sender requirements explicitly state that bulk senders must authenticate emails using SPF, DKIM, and DMARC to ensure messages are delivered and not flagged as spam.
• Spam rate threshold: Maintaining a very low spam complaint rate, specifically below a certain threshold (e.g., 0.3% for Gmail), is a critical factor for avoiding blocks and maintaining good sender reputation.
• Easy unsubscription: Providing a clear and easy one-click unsubscribe option is a mandatory requirement for bulk senders to prevent recipients from marking emails as spam.
• IP warming strategy: Documentation consistently advises a gradual increase in sending volume to engaged users during IP warming to build trust and avoid triggering spam filters.

Key considerations

• Adhere to sender guidelines: Strictly follow the latest Gmail and Yahoo sender guidelines to ensure compliance and avoid blocks.
• Leverage monitoring tools: Utilize Postmaster Tools and similar resources to gain visibility into your sender reputation and identify potential issues early.
• Verify authentication setup: Regularly verify that your DMARC, SPF, and DKIM records are correctly configured for all sending domains, including those within SFMC.
• Continuous list hygiene: Maintaining a clean and engaged subscriber list is paramount, as documentation repeatedly links poor list quality to deliverability issues and IP blocklists.