Summary
Switching to a new Email Service Provider (ESP) necessitates a methodical IP warm-up process to establish a positive sending reputation with Internet Service Providers (ISPs). This critical practice involves beginning with very low sending volumes to highly engaged subscribers and gradually increasing email volume over several weeks. Consistency, patience, and meticulous monitoring of deliverability metrics are paramount to avoid deliverability issues and build trust effectively.
Key findings
- Start Small, Scale Gradually: Begin with very low email volumes, such as 500 emails on the first day, instead of hundreds of thousands. Increase daily volume by a controlled percentage, typically 30% to 50%, with 40% often recommended as a safer rate to avoid sudden, drastic jumps.
- Target Engaged Subscribers First: Prioritize sending to your most active and engaged subscribers initially, as their positive interactions like opens and clicks signal good reputation to Internet Service Providers. Gradually expand to less active segments over time.
- Consistent Sending is Key: Maintain a consistent sending schedule, even if sending small batches daily. Erratic sending patterns or large volume spikes can trigger spam filters and damage your new IP's reputation.
- Monitor Deliverability Metrics Closely: Diligently track key metrics such as open rates, click-through rates, bounce rates, and especially spam complaint rates. Aim for preferably nonexistent complaints to ensure a smooth transition and build trust.
- Utilize Your Own Domain: Always use and sign with your own domain for sending, as building reputation on your domain is crucial. Dismiss any advice from an ESP suggesting the use of their domain, as shared IP reputation is less significant in many B2C contexts.
- Ensure Diverse Domain Exposure: From day one, ensure your initial sends include a mix of different email domains, such as Gmail, Outlook, and Yahoo. This helps ISPs recognize your traffic as legitimate across various providers.
- Quality Content Drives Reputation: Sending relevant, high-quality, and engaging email content is as important as managing volume. Positive recipient engagement reinforces a good sending reputation with ISPs, leading to better deliverability.
Key considerations
- Patience is Essential: The IP warm-up process takes time, typically several weeks, and cannot be rushed. Hasty increases in volume can lead to poor deliverability or even blacklisting.
- New IP Still Needs Warm-up: Even when switching to a new shared IP/domain combination, a warm-up is still required, though it might be a shorter process compared to warming up a completely cold, dedicated IP.
- Avoid Spam Traps: Maintaining a clean email list and actively working to avoid spam traps is crucial to ensure a positive sending history and prevent reputation damage during the warm-up period.
- Vigilance with ESP Advice: While Email Service Providers provide infrastructure, the responsibility for a successful warm-up largely rests on the sender following best practices. Be wary of ESPs that suggest aggressive or technically unsound warm-up plans, such as starting with excessively high volumes.
What email marketers say
10 marketer opinions
To successfully migrate email sending to a new ESP, a strategic IP warm-up is indispensable. This process focuses on systematically building a strong sending reputation with Internet Service Providers (ISPs) by introducing email volume incrementally. It involves a disciplined approach of starting with small, consistent sends to highly engaged segments, meticulously observing performance indicators, and steadily scaling up, which ultimately safeguards deliverability and fosters ISP trust.
Key opinions
- Initial Volume Control: Start with very modest email volumes, such as 500 emails on day one, as a foundation for gradually increasing your sending reputation with ISPs, contrasting sharply with overly ambitious initial sends.
- Gradual Volume Scaling: Implement a controlled daily volume increase, typically between 30% and 50%, with 40% suggested as a secure rate, to avoid triggering spam filters and maintain a predictable sending pattern.
- Prioritize Engaged Audiences: Begin all warm-up efforts by targeting your most active and engaged subscribers, leveraging their positive interactions-opens and clicks-to signal healthy sending practices to ISPs and quickly establish trust.
- Consistent Sending Rhythm: Maintain a steady and consistent email sending frequency, even for smaller batches daily, as erratic or sudden volume surges can severely undermine your new IP's reputation and lead to deliverability issues.
- Comprehensive Metric Monitoring: Continuously track essential deliverability metrics including open rates, click-through rates, bounce rates, and crucially, aim for minimal or nonexistent spam complaints, which are critical indicators of your sending health.
- Dedicated Domain Usage: Always send and authenticate emails using the new domain that is actively undergoing the warm-up process, as this directly contributes to building its unique reputation with mail providers.
- Diverse Domain Exposure: From the outset, ensure your email campaigns reach a varied mix of major email domains, such as Gmail, Outlook, and Yahoo, helping ISPs broadly recognize and legitimize your outgoing traffic.
- Content Relevance and Quality: Recognize that sending high-quality, relevant, and engaging content is just as vital as managing volume. Compelling content encourages recipient interaction, further enhancing your new IP's standing with ISPs.
Key considerations
- Embrace Patience: Understand that a successful IP warm-up is a marathon, not a sprint, requiring several weeks of patient and systematic effort. Rushing the process significantly increases the risk of deliverability setbacks.
- Cautious ESP Guidance: Exercise discernment when evaluating advice from Email Service Providers regarding warm-up strategies; overly aggressive or technically unsound recommendations, such as starting with exceptionally high volumes, should be approached with caution.
Marketer view
Email marketer from Email Geeks explains that starting with 500,000 emails on a new dedicated IP for the first send is far too much, recommending starting at 500 emails on the first day instead.
25 Mar 2025 - Email Geeks
Marketer view
Email marketer from Email Geeks advises against the proposed warm-up plan, recommending starting with 500 emails and increasing daily volume by 30% to 50%, with 40% being a safer recommendation. He stresses the importance of consistently monitoring the new domain's reputation and campaign performance, ensuring complaints are preferably nonexistent. Sebastian also highlights the necessity of always signing with the new domain that is being warmed up.
3 Apr 2024 - Email Geeks
What the experts say
3 expert opinions
Establishing strong email deliverability when transitioning to a new Email Service Provider requires a strategic IP warm-up, a meticulous process of gradually increasing sending volume. This involves beginning with highly engaged subscribers to build a positive sending history, emphasizing a sender's own domain for reputation, and vigilantly monitoring key metrics to ensure trust with Internet Service Providers.
Key opinions
- Avoid Aggressive Starts: Starting an IP warm-up with excessively high volumes, such as 500,000 emails on day one, is a clear sign of an ESP's lack of technical and deliverability expertise.
- Engage the Most Active: Initiate sending to your most engaged subscribers, gradually increasing volume over several weeks to systematically build a positive sending history with new IPs.
- Prioritize Own Domain: Using and signing with your own domain is paramount for building reputation, as shared IP reputation holds less significance in B2C contexts, making ESP advice to use their domain highly problematic.
- Sustained Reputation Management: Maintaining a healthy sender reputation requires continuous monitoring of metrics, actively avoiding spam traps, and minimizing bounce rates throughout the warm-up process.
Key considerations
- ESP Competence Warning: Be cautious of ESPs that advise starting with unsustainably high sending volumes, as this indicates a fundamental misunderstanding of proper IP warm-up protocols.
- Shared IP Warm-up Necessity: Even when migrating to a new shared IP/domain combination, a warm-up process is still essential, although its duration might be shorter compared to warming a completely new, dedicated IP.
- Domain Reputation Dominance: In B2C scenarios, your sending domain's reputation is almost universally more critical than the reputation of a shared IP address.
Expert view
Expert from Email Geeks explains that starting with 500,000 emails for the first day of IP warm-up is extremely high and indicates a lack of technical and deliverability competence from the ESP. She clarifies that a new shared IP/domain combination still requires warming up, though it might be a shorter process than a cold IP. Laura emphasizes that using the client's own domain is crucial and dismisses the ESP's advice to use their domain as 'horrible advice', noting that shared IP reputation is almost irrelevant in B2C contexts.
25 Dec 2021 - Email Geeks
Expert view
Expert from Spam Resource explains that IP warm-up involves gradually increasing sending volume over time, starting with the most engaged recipients. They emphasize the importance of maintaining a good reputation by avoiding spam traps and minimizing bounce rates during the warm-up period, which is crucial when switching to a new ESP and new IPs.
3 Jun 2022 - Spam Resource
What the documentation says
5 technical articles
When migrating email sending to a different Email Service Provider (ESP), a disciplined IP warm-up strategy is fundamental to cultivating a strong sending reputation with Internet Service Providers (ISPs). This systematic approach involves initiating sends with minimal volumes to the most active segments of your audience, incrementally expanding both email volume and the diversity of recipient domains over several weeks. Continuous vigilance over key performance metrics is essential for adapting the sending pace and ensuring successful deliverability.
Key findings
- Gradual Volume Scaling: Consistently increasing email volume in measured increments is crucial for building a positive sending reputation without triggering spam filters.
- Engaged Audience Priority: Begin the warm-up by sending to your most engaged and active subscribers, as their positive interactions signal trustworthiness to ISPs.
- Reputation Establishment: The primary goal of IP warm-up is to systematically establish a robust sending reputation with Internet Service Providers, paving the way for consistent deliverability.
- Performance Metric Oversight: Diligently monitor crucial metrics like bounce rates, spam complaints, and engagement levels to adjust your sending strategy and identify potential issues early.
- Patience and Consistency: Success hinges on patience and maintaining a consistent sending schedule over several weeks, as rushing the process can severely jeopardize deliverability and lead to blacklisting.
- Diverse Domain Exposure: Ensure your initial and subsequent sends reach a wide array of email domains, such as Gmail, Outlook, and Yahoo, to help ISPs broadly legitimize your traffic.
Key considerations
- Risk of Hasty Expansion: Accelerating the warm-up process too quickly can result in significant deliverability issues, including emails being flagged as spam or even IP blacklisting.
- Multi-Week Commitment: The warm-up period is not instantaneous, typically requiring several weeks of dedicated effort to build and solidify a positive sending reputation.
- Continuous Monitoring Imperative: Ongoing vigilance of performance metrics is crucial not just for initial adjustments but throughout the entire warm-up phase to maintain healthy sending.
Technical article
Documentation from SendGrid Docs explains that a new IP address needs gradual warm-up, starting with low volumes of highly engaged subscribers and slowly increasing volume and diversity over several weeks to build a positive sending reputation. This is crucial when migrating to a new ESP to avoid deliverability issues.
25 Apr 2025 - SendGrid Docs
Technical article
Documentation from Mailchimp Knowledge Base shares that when switching to a new ESP, IP warm-up is essential to establish a good sending reputation with ISPs. They recommend starting with your most engaged contacts and progressively increasing email volume and audience segments over time, closely monitoring performance.
11 Apr 2023 - Mailchimp Knowledge Base
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