Summary
During an email service provider (ESP) migration and IP warmup, the consensus among deliverability experts and documentation from leading ESPs is to continue sending emails from the old platform. This strategy involves a gradual, phased approach: progressively decreasing the email volume sent from the previous ESP while simultaneously increasing it on the new one. This method is critical for smoothly transferring sender reputation, preventing deliverability issues, and ensuring business continuity, especially for high-volume senders. The overlap period can vary significantly, lasting from several weeks to many months, providing a controlled environment to establish trust with internet service providers and avoid being flagged for unusual sending patterns by blocklists or blacklists. Furthermore, maintaining the old ESP for a period offers a valuable backup and allows for crucial data comparison to monitor the new platform's performance.
Key findings
- Gradual volume shift is crucial: It is universally recommended to slowly decrease sending volume from the old ESP while simultaneously increasing it on the new one during the IP warmup period. This gradual 'ramp up' strategy is essential for establishing a strong sending reputation with internet service providers.
- Maintains sender reputation: This phased approach allows for a smooth transfer of sender reputation to the new IP addresses. Attempting an abrupt switch can lead to deliverability problems, as mailbox providers need time to recognize and trust a new sending infrastructure.
- Ensures business continuity: For larger clients or those with significant revenue tied to email campaigns, continuing to use the old platform prevents immediate revenue impacts and ensures uninterrupted email communication. It acts as a bridge during the migration.
- Provides backup and data: Maintaining the old provider for a period offers a reliable backup solution in case of unexpected issues with the new platform. It also provides valuable comparative data for measuring the success and performance of the new ESP during its initial phase.
- Overlap duration varies: The period of overlap between using both ESPs can range from a few weeks to almost nine months, depending on the email volume, audience engagement, and specific migration requirements. This flexible timeframe allows for thorough testing and reputation building.
Key considerations
- Implement a phased migration: Do not switch off the old email service provider (ESP) abruptly. Instead, adopt a gradual 'ramp up' strategy for the new platform, progressively shifting email volume. This approach allows for a controlled transition, ensuring a smooth transfer of sender reputation.
- Monitor performance closely: During the transition, observe the deliverability and recipient engagement rates from the new ESP. This allows for observation of performance and recipient reactions, which is crucial for ensuring optimal inbox placement and making any necessary adjustments.
- Synchronize opt-outs: Continuously synchronize suppression lists and opt-outs between the old and new platforms. This is essential to honor recipient preferences and avoid complaints or issues that could negatively impact your sender reputation on both blocklists and blacklists.
- Assess link longevity: Determine how long links from the old platform will remain active after contract termination. If they cease to function immediately, sending should be stopped from the old platform before that time. If they continue for several months, deliverability monitoring of those older links becomes a primary concern.
- Plan for potential overlap: Be prepared for a significant period where both old and new sending solutions are active. This overlap can range from several weeks to many months, especially for larger clients where revenue impacts prevent an abrupt halt to sending from the previous platform.
What email marketers say
10 marketer opinions
When migrating to a new email service provider (ESP) and undertaking the crucial IP warmup phase, it is overwhelmingly recommended to maintain simultaneous sending from your old platform. This dual-platform strategy is not merely an option, but often a necessity, particularly for enterprises where revenue depends heavily on uninterrupted email communication. The approach involves a meticulous, phased transition: slowly reducing the email volume dispatched from the legacy ESP while concurrently ramping up sending on the new one. This ensures a seamless transfer of sender reputation and mitigates the risk of deliverability challenges, such as being flagged by blocklists or blacklists, by presenting consistent sending patterns to internet service providers. Furthermore, retaining the old ESP for an interim period provides a crucial safety net and offers valuable comparative data to gauge the new platform's effectiveness.
Key opinions
- Mandatory overlap: For a smooth transition, and particularly for high-volume senders, continuing to send from your old email service provider (ESP) during migration and warmup is considered essential. This prevents abrupt changes that could harm deliverability and ensures business continuity.
- Phased volume adjustment: The core strategy involves a systematic decrease in email volume from the previous ESP while simultaneously increasing it on the new platform. This gradual ramp-up allows internet service providers to slowly build trust in the new sending infrastructure.
- Protects sender reputation: An abrupt cessation of sending from a trusted domain, coupled with a sudden surge from a new one, can severely damage sender reputation. A phased approach safeguards your reputation, preventing issues like being flagged by blocklists (or blacklists).
- Offers data and safety net: Keeping the old ESP active provides valuable historical data for performance comparison and acts as a vital backup. This allows for assessment of the new platform's success while offering a fallback option should unforeseen issues arise.
- Flexible transition timeline: The duration of this overlap can range from a few weeks to several months, with some migrations extending up to nine months. The timeline is flexible and depends on the scale of email operations and the specific requirements of the warmup process.
Key considerations
- Avoid abrupt changes: It is crucial not to suddenly halt sending from your existing email service provider. Instead, implement a gradual 'ramp up' on the new platform, systematically shifting email volume to avoid deliverability shocks.
- Maintain opt-out synchronization: During the overlap, ensure that opt-outs and suppression lists are consistently synchronized between both the old and new platforms. This prevents sending to unsubscribed recipients, which can lead to complaints and negatively impact your sender reputation, potentially landing you on a blocklist (or blacklist).
- Monitor performance metrics: Continuously track key deliverability metrics, such as open rates, click-through rates, and bounce rates, for emails sent from both platforms. This monitoring helps you assess the new platform's performance and make data-driven adjustments.
- Strategically shift audience: Consider initially migrating your most engaged segments or 'best traffic' to the new ESP. This helps build a positive sender reputation quickly, as these recipients are more likely to open and interact with your emails.
- Allocate resources for overlap: Be prepared for the operational and potentially financial implications of running two ESPs concurrently for an extended period. This overlap is a critical investment in ensuring a successful migration and protecting your email program's integrity.
Marketer view
Marketer from Email Geeks explains that most folks operate both platforms in tandem while warming up. This is often necessary for larger clients where revenue impacts prevent stopping one platform. Typically, you should bleed the best traffic over to the new ESP first.
14 Dec 2024 - Email Geeks
Marketer view
Marketer from Email Geeks explains that while sometimes it is not possible, they recommend a new client migrating keeps their other provider for a couple of months. This provides a backup and valuable data for warmup and success measurement on the new platform. It is also important to properly keep opt-outs in sync between the two platforms to ensure a smooth warmup.
11 Nov 2022 - Email Geeks
What the experts say
3 expert opinions
The consensus among deliverability experts emphasizes a strategic continuation of email sending from an old email service provider (ESP) during the transition to a new platform and its subsequent warmup period. This approach is not about immediately shutting down the old system, but rather implementing a controlled, phased migration. By gradually shifting a percentage of email volume from the established ESP to the new one, businesses can meticulously observe how the new infrastructure performs and how recipients react to messages sent from it. This method facilitates a smoother transfer of sender reputation and is vital for avoiding deliverability pitfalls, such as being flagged by a blocklist or blacklist. A practical consideration during this overlap includes understanding the operational lifespan of links generated by the old platform, as their cessation could impact user experience.
Key opinions
- Gradual transition is vital: Experts advocate for a gradual ramp-up of sending from the new email service provider (ESP) while the old one remains active. This avoids an abrupt 'light switch' cutover, which can negatively impact deliverability.
- Performance observation: Sending a segment of mail from the new provider before full commitment allows for critical observation of its performance and how recipients respond. This period of parallel operation is essential for making informed adjustments.
- Recipient reaction insights: Monitoring initial sends from the new ESP provides direct insight into recipient reactions, enabling adjustments to sending patterns or content before a complete migration to ensure optimal inbox placement.
- Sender reputation continuity: A phased shift helps in maintaining and smoothly transferring sender reputation to the new IP addresses, mitigating risks of being flagged by a blocklist (or blacklist) during the warmup process.
- Link longevity consideration: The operational lifespan of links generated by the old ESP post-contract termination is a critical factor; if they expire quickly, sending from the old platform should cease beforehand to prevent broken links.
Key considerations
- Implement phased volume transfer: Gradually shift email volume, perhaps starting with small percentages (e.g., 10-20%) every few days, from the old ESP to the new one. This ensures a controlled warmup for the new sending infrastructure.
- Closely monitor new ESP's performance: Actively track deliverability rates, engagement metrics, and any negative feedback for emails sent through the new provider. This allows for timely adjustments and risk mitigation during the transition.
- Assess old link validity: Confirm how long links from your previous email service provider will remain functional after you stop sending from it. Plan accordingly, as broken links can negatively impact user experience and engagement.
- Maintain parallel sending: Be prepared to operate both the old and new email service providers concurrently for a period. This overlap is crucial for testing, reputation building, and a smooth transition without abrupt deliverability shocks.
- Prioritize recipient experience: Ensure a seamless experience for your subscribers throughout the migration. This includes consistent branding and functional links, regardless of which ESP sent the email, to maintain trust and engagement.
Expert view
Expert from Email Geeks raises a side note regarding how long links from the old platform will continue to operate after leaving. If they stop working the moment the contract ends, sending should cease before that time. If they continue for 6-12 months, deliverability monitoring becomes the primary concern.
19 Mar 2023 - Email Geeks
Expert view
Expert from Spam Resource explains that during an ESP migration, it's wise to start sending a segment of your mail from the new provider before fully committing. This allows observation of performance and recipient reactions from the new provider, implying a period where both old and new ESPs are active and sending. This gradual approach allows for a controlled transition rather than an abrupt switch.
5 Jun 2023 - Spam Resource
What the documentation says
5 technical articles
During the critical phase of migrating to a new email service provider (ESP) and warming up new IP addresses, industry best practices and leading ESPs consistently recommend maintaining active sending from the old platform. This strategy involves a systematic and gradual transition where email volume is progressively decreased from the legacy ESP while concurrently being increased on the new infrastructure. This deliberate 'phasing out' of the old and 'ramping up' of the new is essential for effectively transferring sender reputation, ensuring a seamless user experience, and preventing potential deliverability issues that could arise from sudden changes, such as being placed on a blocklist or blacklist.
Key findings
- Gradual volume shift: All sources emphasize a progressive reduction in email volume from the old ESP, coupled with a simultaneous increase on the new one, as the cornerstone of the transition process. This ensures a measured and controlled migration.
- Reputation transfer: This phased approach is crucial for successfully transferring existing sender reputation to new IP addresses, allowing internet service providers to slowly build trust in the new sending infrastructure and prevent blacklisting (or blocklisting).
- Concurrent operation: For a successful migration, sending from both the old and new ESPs concurrently is necessary, creating an overlap period during which the transition occurs. This parallel operation minimizes disruption.
- Avoid abrupt changes: An sudden cessation of sending from an established platform can negatively impact deliverability, making the gradual decrease a protective measure against issues like being flagged by a blocklist (or blacklist).
Key considerations
- Careful volume management: Meticulously plan and execute the gradual reduction of email volume from the old ESP, ensuring it aligns with the warming schedule of the new IPs. This precision prevents unintended deliverability issues.
- Monitoring reputation transfer: Closely observe deliverability and engagement metrics from the new platform to confirm that sender reputation is being successfully established and maintained. This vigilance helps ensure a smooth transition.
- Phased audience migration: Consider segmenting your audience and gradually shifting them to the new platform, perhaps starting with highly engaged users, to build positive signals and trust with internet service providers early on.
- Operational readiness: Ensure your team is prepared to manage email campaigns across two distinct platforms during the overlap period, including tasks like list synchronization, content deployment, and performance monitoring.
Technical article
Documentation from Mailgun explains that during the process of warming up a new IP address, you should gradually decrease the email volume sent from your old IP while simultaneously increasing it on the new IP until the transition is complete.
20 Jul 2023 - Mailgun
Technical article
Documentation from SendGrid shares that as you warm up new IPs, you should progressively increase the email volume sent via SendGrid while decreasing the volume from your previous sending solution, which effectively transfers your sender reputation.
1 Oct 2021 - SendGrid
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