Summary
Migrating to a new Email Service Provider (ESP) can often lead to a temporary drop in email deliverability, a common phenomenon in the email marketing world. This initial decline is primarily due to the need to build a new sender reputation with mailbox providers (ISPs) from the ground up, as the new ESP's IP addresses and sending domains might not have the same established trust as your previous provider.
Key findings
- Temporary drop: Deliverability often falls immediately after switching ESPs and can take anywhere from 3 to 6 months to fully recover as a new sender reputation is established. This is a normal part of the process of IP and subdomain warming.
- Data discrepancies: The definition of "delivered" can vary significantly between ESPs. Some might count an email as delivered once it enters their outbound queue, while others might only count it after successful acceptance by the recipient's mail server. This difference can lead to perceived drops that are merely reporting discrepancies, rather than actual deliverability issues.
- Reputation building: The core issue often lies in building a new reputation. A significant factor is how thoroughly a sending list was cleaned pre-migration. Any undeliverable addresses (like invalid emails or spam traps) sent from a new IP or subdomain can rapidly harm reputation and trigger rate-limiting.
- ISP-specific issues: Deliverability issues are often not universal but concentrated at specific mailbox providers, such as Gmail. This indicates a need for granular reporting and targeted troubleshooting.
Key considerations
- Understand ESP metrics: Before migrating, thoroughly understand how your new ESP calculates and reports metrics like "delivered percentage" to avoid misinterpreting data. This can help set realistic expectations for your transition.
- Detailed reporting: Ensure your new ESP provides detailed failure data, including bounce logs, block types, and deferral reasons, ideally broken down by ISP. This granular information is crucial for pinpointing the exact nature of deliverability issues. Without it, diagnosing email deliverability issues becomes significantly harder.
- Proactive list hygiene: Clean your email list thoroughly before migration by removing known invalid, bounced, unsubscribed, or low-engagement addresses. This significantly reduces the risk of hitting spam traps or generating complaints, which can severely damage your new sending reputation. A comprehensive guide can be found at Dyspatch's ultimate guide to switching ESPs.
- Warm-up strategy: Implement a structured IP warming plan to gradually increase sending volume. Blasting high volumes from a new subdomain or IP without proper warming is a common cause of deliverability drops.
- Support engagement: If metrics are unclear or issues persist, engage with your new ESP's support team. They can provide insights into their reporting methods and help diagnose underlying problems.
What email marketers say
Email marketers frequently share experiences of fluctuating deliverability after migrating ESPs. While some anticipate a temporary dip, others are surprised by persistent issues. The core of their discussions revolves around understanding reporting differences, the importance of pre-migration list hygiene, and the challenges of reputation building on a new platform.
Key opinions
- Anticipate a drop: Many marketers expect an initial decrease in deliverability when moving ESPs. This is often seen as a normal part of the process, with a general expectation of recovery over several months.
- Metric interpretation: There's a consensus that the meaning of "delivered" can vary significantly between ESPs, leading to confusion. A drop might not signify an actual deliverability issue, but rather a different way of calculating success rates.
- SendGrid's reputation: Marketers generally view SendGrid as a reputable ESP, suggesting that any persistent deliverability issues are unlikely to be inherent to the platform itself, but rather related to sender practices or data quality.
- Lack of detailed reporting: Frustration is often expressed over ESP interfaces that only provide high-level numbers (requests, delivered, bounces) without granular breakdowns by ISP or specific failure reasons, hindering effective diagnosis.
Key considerations
- Seek specific failure data: Actively seek out more detailed reporting from your ESP, such as breakdowns by inbox provider (e.g., Gmail, Outlook), bounce logs, or block codes. This data is essential for diagnosing the specific causes of deliverability drops, especially when migrating. More information on how to get SMTP bounce logs can be found in our knowledge base.
- Verify suppression: Ensure that bounces, unsubscribes, and complaints are being properly suppressed by the new ESP. A declining delivered percentage could simply be a reflection of the ESP actively suppressing problematic addresses over time.
- Contact ESP support: When internal reporting is insufficient, contact your ESP's support team for clarification on metrics and to troubleshoot potential issues. They can offer insights specific to their platform's data interpretation.
- Monitor blocklists: An uptick in blocks or bounces can indicate a blacklist (or blocklist) issue. Regularly monitor your IP and domain status on major blacklists.
Email marketer from Email Geeks notes that deliverability often falls when moving platforms and can take 3 to 6 months to recover. This is a common and expected phase as the sending infrastructure builds new trust with mailbox providers. Understanding this timeframe is crucial for setting realistic expectations and avoiding unnecessary panic during the migration period. It emphasizes the importance of a well-planned IP warming strategy.
Email marketer from Email Geeks observed a delivered percentage drop from 99.78% to 94.21% over several months after migrating to SendGrid, with Gmail addresses being the biggest issue. This specific example highlights the real-world impact of ESP migration on deliverability metrics. The pattern of a gradual decline suggests a potential reputation issue being built over time, rather than an immediate hard block. It also points to the need for ISP-specific monitoring.
What the experts say
Email deliverability experts emphasize that a drop in email deliverability after an ESP migration is a common occurrence. They highlight the complexities of sender reputation, the nuances of ESP reporting, and the critical role of list management and IP warming in achieving stable deliverability on a new platform.
Key opinions
- Reputation reset: Deliverability typically experiences an initial decrease after moving ESPs, then gradually returns to normal. This is because a new sending reputation needs to be established for the new IP addresses or subdomains.
- ESP 'delivered' definition: The metric "delivered" can mean different things across ESPs. For some, it might mean the email entered the outbound queue, while others might count it only after successful acceptance by the recipient's Mail Transfer Agent (MTA).
- Not ESP's fault: For reputable ESPs like SendGrid, sustained deliverability issues are rarely due to the platform itself. Instead, they often stem from how the sender manages their data or email program during the early stages of reputation building.
- Root cause analysis: The gap between requested and delivered emails needs to be investigated by looking at bounces, blocks, and deferrals, ideally at the ISP level. This allows for a precise diagnosis of the problem.
Key considerations
- Detailed reporting is key: Access to specific failure data (bounce codes, block reasons, deferrals) and ISP-level reporting is crucial for diagnosing issues. If your ESP's interface lacks this, push for more detailed logs or reports to understand why emails are going to spam.
- Proactive list hygiene: Before migrating, aggressively suppress all known invalids, complaints, and unengaged subscribers. Attempting to send to undeliverable addresses from a new IP can quickly lead to rate-limiting and damage your new reputation, often resulting in temporary bounces.
- Implement a proper warm-up: Ensure you follow a proper IP and domain warming schedule. Blasting high volumes to a new subdomain or IP without gradually building trust with ISPs is a primary reason for deliverability plummeting. This process helps ISPs recognize your sending patterns as legitimate.
- Review authentication: Verify that SPF, DKIM, and DMARC records are correctly configured for your new sending domain and ESP. Misconfigurations can lead to authentication failures and direct emails to spam folders. For more details, see a simple guide to DMARC, SPF, and DKIM.
- Consult google postmaster tools: Leverage tools like Google Postmaster Tools to gain insights into your sender reputation, spam rates, and delivery errors specifically for Gmail, as these provide direct feedback from the ISP. A useful external resource is Email vendor selection's perspective on deliverability plummeting initially.
Expert from Email Geeks clarified that there are cases where a reported "delivered" percentage might decrease over time due to how an ESP calculates the number, rather than an actual drop in accepted mail. This suggests that the issue might be one of reporting methodology. It means marketers should delve into the exact definition of metrics within their new ESP to ensure they are comparing apples to apples, not just assuming a decline in performance.
Expert from Email Geeks stated that they generally expect to see an initial decrease in deliverability after moving ESPs, followed by a return to normal rates. This reinforces the idea of a temporary reputation reset during migration. It implies that while a dip is common, a sustained drop without recovery points to deeper underlying issues that need to be addressed beyond just the platform change.
What the documentation says
Official documentation and industry standards provide a foundational understanding of email deliverability, particularly concerning new sender reputations and migration. These resources emphasize the technical protocols, best practices for IP warming, and the importance of data quality as critical factors influencing inbox placement.
Key findings
- Sender reputation: ISPs assign a reputation score to sending IPs and domains based on historical sending behavior, complaint rates, bounce rates, and engagement. When migrating to a new ESP, this reputation essentially resets, necessitating a careful warming process to build trust.
- IP warming protocols: Official guidelines recommend gradually increasing email volume over a period (weeks to months) to establish a positive sending history with major mailbox providers. Rapid increases can trigger spam filters and lead to blocks.
- Authentication standards: Proper configuration of email authentication protocols (SPF, DKIM, DMARC) is fundamental. These standards help verify the sender's identity and prevent spoofing, playing a crucial role in initial inbox placement for new senders.
- List quality impact: Sending to invalid or low-quality addresses, especially during the warming phase, can quickly lead to high bounce rates and spam trap hits, severely damaging the new sender reputation and leading to blocklisting (or blacklisting).
Key considerations
- Pre-migration data audit: Before moving, clean your subscriber list meticulously. Remove unengaged subscribers, hard bounces, and any known spam trap addresses to ensure you start with the highest quality data on your new ESP. This proactive step significantly reduces deliverability risks.
- Align authentication: Ensure your new ESP fully supports and guides you through the proper setup of SPF, DKIM, and DMARC records for your sending domain. These are non-negotiable for modern email deliverability and are crucial for how SPF, DKIM, and DMARC affect email deliverability when using a third-party ESP.
- Monitor postmaster tools: Actively monitor postmaster tools (e.g., Google Postmaster Tools, Outlook SNDS) provided by major ISPs. These tools offer critical data on your new IP/domain reputation, spam rates, and delivery errors, allowing for timely intervention. Check out our ultimate guide to Google Postmaster Tools V2.
- Compliance with new regulations: Stay informed about evolving sender requirements from major mailbox providers, such as those introduced by Google and Yahoo in early 2024. Non-compliance can lead to severe deliverability penalties. SocketLabs offers a survival guide for ESP migration that covers key facets including compliance.
Documentation from RFC 5321 (SMTP) specifies how mail servers communicate and handle transient and permanent errors. This foundational protocol dictates how bounces and deferrals are reported back to the sender. Understanding these SMTP response codes is crucial for diagnosing why emails are not being accepted by recipient servers, especially during the early stages of an ESP migration when new IPs might face initial rate-limiting or soft bounces.
Documentation from the CSA (Certified Senders Alliance) outlines best practices for senders to maintain good sender reputation. It emphasizes that consistent sending patterns, low complaint rates, and proper list hygiene are critical for deliverability. When migrating ESPs, adhering to these established best practices is paramount to building a new positive reputation quickly and avoiding common pitfalls that lead to deliverability drops, like sending to old, unengaged lists.
