Does segmenting email sends by provider improve deliverability for transactional emails?

Key findings

• Automated queues: Reputable Email Service Providers (ESPs) have sophisticated Message Transfer Agents (MTAs) that automatically manage email queues and distribute mail to various mailbox providers (MBPs) at optimal rates, negating the need for manual segmentation.
• Independent systems: Mailbox provider systems (e.g., Gmail, Yahoo, Hotmail/Outlook) operate independently and do not share data or communicate with each other regarding sender reputation or email flow. Your deliverability to one does not directly impact the other's system in this manner.
• Transactional nature: Transactional emails are typically user-initiated and time-sensitive. Attempting to segment them by provider for sequential sending can introduce unnecessary delays and complexity, potentially impacting the user experience. For more on this, read about how to troubleshoot transactional emails going to spam.
• Focus on content and engagement: Factors like sender reputation, email content quality, recipient engagement, and adherence to authentication protocols (SPF, DKIM, DMARC) are far more impactful on deliverability than provider-based segmentation. Understanding how Internet Service Providers track email engagement is crucial.

Key considerations

• Trust your ESP: If you are using a reliable transactional email service provider, they are already equipped to manage delivery rates and volume to ensure optimal inbox placement across various MBPs.
• Maintain separate streams: It remains a best practice to keep your transactional email stream separate from your marketing email stream, ideally using different IP addresses or subdomains, to protect the reputation of your critical transactional communications. This is a common strategy to improve email deliverability.
• Monitor deliverability metrics: Instead of manual segmentation, focus on monitoring key deliverability metrics such as open rates, click-through rates, bounce rates, and complaint rates via your ESP's analytics or a dedicated deliverability platform.
• Authentication standards: Ensure your SPF, DKIM, and DMARC records are correctly configured. These authentication methods are fundamental to building trust with mailbox providers and ensuring your emails are delivered, regardless of specific provider queuing.

Key opinions

• No direct benefit: Many marketers believe there is no direct deliverability benefit from segmenting sends by email provider, as mailbox providers operate independently.
• ESPs handle routing: Reliable ESPs automatically manage the intricate details of distributing mail to various MBPs at acceptable rates, making manual intervention unnecessary.
• Focus on core deliverability: Marketers prioritize fundamental best practices such as maintaining strong sender reputation, ensuring high engagement, and adhering to email authentication standards over provider-specific sending order.
• Transactional email definition: There's a shared understanding that transactional emails are primarily triggered by user actions, even if the delivery isn't instantaneous.

Key considerations

• Leverage ESP capabilities: Utilize your ESP's built-in capabilities for managing email distribution, as they are optimized for performance and deliverability. This also applies to managing email sending speed.
• Focus on user experience: Prioritize timely delivery of transactional emails to ensure a positive user experience, rather than implementing complex segmentation that may delay delivery. This is key to improving deliverability for transactional emails.
• Separate email streams: Maintain distinct sending streams for transactional and marketing emails to prevent issues with one from affecting the other, especially if using a dedicated IP address. Consider whether separate IPs are necessary for transactional emails.
• Monitor engagement: High engagement (opens, clicks) for transactional emails can positively influence your overall sender reputation, making it more important to focus on relevant, timely content than provider-specific queues.

Key opinions

• No practical benefit: Experts agree there's no inherent deliverability benefit to ordering sends by provider for transactional mail.
• Definition of transactional: A common understanding is that transactional emails are typically a direct result of a user action, even if the delivery has a slight delay.
• ESPs handle technicalities: Robust ESPs automate the process of managing throughput to different MBPs, which is superior to any manual attempt at provider-based segmentation.
• Inter-ISP communication: Mailbox providers do not share reputation data or internal systems, so influencing one by how you send to another isn't a viable strategy.

Key considerations

• Prioritize authentication: Focus on proper implementation of authentication protocols like SPF, DKIM, and DMARC, as these are critical for establishing sender trust with MBPs. Learn more with a simple guide to DMARC, SPF, and DKIM.
• Maintain sender reputation: The primary driver for deliverability is your sender reputation, which is built on consistent sending practices, low complaint rates, and high engagement. This includes understanding how email sending practices impact domain reputation.
• Monitor blocklists: Regularly check if your sending IPs or domains are listed on any public or private blocklists, as this will significantly impact deliverability more than sending order.
• Consistent sending: Consistent sending volume and patterns help build trust with MBPs. Drastic changes or artificial segmentation patterns are generally not recommended.

Key findings

• Stream separation: Documentation frequently advises keeping marketing and transactional email streams separate to protect the deliverability of critical communications. This can be achieved through different IPs, subdomains, or ESPs. Further insights are available regarding why use subdomains for email marketing deliverability.
• Authentication is key: Strong email authentication (SPF, DKIM, DMARC) is consistently listed as a top priority for establishing sender credibility and ensuring emails reach the inbox. This applies to all email types.
• Engagement metrics: High open rates and click-through rates, typical for transactional emails, are highlighted as positive signals that can improve overall sender reputation. Conversely, bounces and spam complaints harm reputation, regardless of recipient provider.
• No provider-specific order: There is no mention of a recommended practice to segment sends by recipient mailbox provider to improve deliverability for transactional emails.

Key considerations

• Optimize content: Even for transactional emails, clear, concise, and relevant content is vital to encourage engagement and reduce the likelihood of being marked as spam.
• Reputable ESPs: Using an established and reliable ESP is crucial, as they manage the technical complexities of delivery, including IP warming, throttling, and ISP-specific nuances. Consider how this impacts how email deliverability works.
• Monitor performance: Regularly review deliverability reports and feedback loops to identify and address any potential issues promptly. Tools like Google Postmaster Tools provide valuable insights.
• Adhere to ISP guidelines: Always follow the best practices and sender guidelines provided by major mailbox providers, as these directly influence their filtering decisions.