Summary
The consensus among experts, email marketers, and documentation sources is that you should continue sending emails from your old ESP while warming up a new IP address. Overlapping the use of both ESPs is a best practice for maintaining a consistent sending presence, preventing a sudden drop in email volume, and preserving your sending reputation. Focus on sending to your most engaged subscribers from the new IP to establish a positive reputation with ISPs, while gradually reducing the volume of emails sent from the old IP. It is crucial to monitor deliverability metrics for both IPs and inform subscribers about the change. Delay moving revenue emails to the new IP until warm up is complete.
Key findings
- Overlap is Key: Overlapping the use of both old and new ESPs is a recommended practice for IP warming.
- Maintain Sending Reputation: Continuing to send from the old ESP helps maintain your overall sending reputation.
- Engaged Subscribers First: Focus on sending to your most engaged subscribers from the new IP to build a positive reputation.
- Gradual Transition: Slowly move subscribers from your old ESP to the new one, reducing volume on the old while increasing on the new.
- Consistent Presence: Maintain a consistent sending presence to avoid sudden drops in email volume, which negatively impacts deliverability.
Key considerations
- Segment Audience: Segment your audience and prioritize sending to your most engaged subscribers from the new IP.
- Monitor Metrics: Continuously monitor deliverability metrics (open rates, bounce rates, etc.) for both IPs.
- Communicate Changes: Inform subscribers about changes to your email sending infrastructure.
- Delay Revenue Emails: Delay moving revenue generating emails over to the new IP until the warm up process is complete.
- Avoid Sudden Stops: Avoid stopping sends from the old ESP entirely to prevent sudden negative impacts on deliverability.
What email marketers say
10 marketer opinions
When warming up a new IP address, it's generally recommended to continue sending emails from your old ESP. This helps maintain a consistent sending presence and avoids a sudden drop in email volume, which can negatively impact deliverability. The key is to transition gradually, overlapping the use of both ESPs. Focus on sending to your most engaged subscribers from the new IP to establish a positive sending reputation, while reducing the volume of emails sent from the old IP over time. Monitoring the performance of both IPs, including open rates and bounce rates, is crucial during this process.
Key opinions
- Maintain Sending Reputation: Continuing to send from your old ESP helps maintain your overall sending reputation during the IP warm-up phase.
- Gradual Transition: A gradual transition, overlapping the use of both ESPs, is crucial for a smooth migration.
- Engagement Focus: Prioritize sending to your most engaged subscribers from the new IP to build a positive reputation with ISPs.
- Volume Reduction: Reduce the volume of emails sent from your old IP over time as the new IP warms up.
- Performance Monitoring: Closely monitor the performance of both IPs, including open rates and bounce rates, to ensure deliverability.
Key considerations
- Audience Segmentation: Segment your audience and prioritize sending to your most engaged subscribers from the new IP.
- Gradual Increase: Gradually increase the volume of emails sent from the new IP over time, while decreasing the volume from the old IP.
- Monitor Metrics: Continuously monitor deliverability metrics (open rates, bounce rates, etc.) for both IPs and adjust your strategy accordingly.
- Avoid Sudden Drops: Avoid stopping sends from the old ESP entirely to prevent a sudden drop in email volume.
- Plan for Overlap: Plan for a period of overlap where you're actively sending from both your old and new ESPs.
Marketer view
Email marketer from Iterable explains that you should segment your audience during IP warm-up. They say you should start by sending to your most engaged subscribers to establish a good reputation with ISPs.
19 Mar 2023 - Iterable
Marketer view
Email marketer from Email Marketing Forum states that it is important to monitor the performance of both IPs, watching open rates and bounce rates of both sets of sends, and if things are going well, slowly ramp down the old IP as the new one increases
20 May 2025 - Email Marketing Forum
What the experts say
6 expert opinions
Experts generally recommend overlapping migration periods when warming up a new IP address with a new ESP. This means continuing to send from your old ESP, focusing on less engaged subscribers or specific types of emails like revenue emails, while sending to the most engaged subscribers from the new IP. Sending a notice to subscribers about the change is also suggested. It is best not to stop sending completely from your old ESP to keep a consistent sending volume.
Key opinions
- Overlap Migration: Overlapping sending from both old and new ESPs is a recommended best practice.
- Segment by Engagement: Send to the most engaged subscribers from the new IP and less engaged from the old IP.
- Delay Moving Revenue Emails: Keep revenue-generating emails on the old IPs until the warm-up process is complete.
- Communicate the Change: Inform subscribers about the change in sending infrastructure.
Key considerations
- Gradual Transition: Avoid abrupt changes in sending volume from either ESP.
- Engagement-Based Segmentation: Carefully segment subscribers based on engagement levels for optimal deliverability.
- Monitor Performance: Continuously monitor deliverability metrics to ensure a smooth transition.
- Focus on Active Users: Focus on the most active and engaged users when sending from the new IP.
Expert view
Expert from Email Geeks suggests sending a notice saying "we are making changes to improve our services, and our [from address / other ] is changing be sure to look out for [new thing] here".
4 Sep 2024 - Email Geeks
Expert view
Expert from Email Geeks recommends starting with the most engaged subscribers on the new IPs and sending to less engaged subscribers from the old IPs, and not letting people forget you.
3 Sep 2024 - Email Geeks
What the documentation says
4 technical articles
Technical documentation from various sources emphasizes the importance of a gradual approach when warming up a new IP address. When transitioning to a new ESP, it's crucial to gradually increase sending volume from the new IP while phasing out the old ESP. Avoiding sudden changes in sending volume is key to maintaining a consistent sending reputation and preventing deliverability issues. Starting with small volumes enables you to monitor deliverability and address any issues that arise.
Key findings
- Gradual Volume Increase: Gradually increasing sending volume from the new IP is essential for establishing a positive sending reputation.
- Phase Out Old ESP: It's crucial to gradually phase out the old ESP while warming up the new IP.
- Consistent Sending Reputation: Maintaining a consistent sending reputation is vital for preventing deliverability issues.
- Avoid Sudden Changes: Sudden changes in sending volume should be avoided to ensure deliverability.
Key considerations
- Monitor Deliverability: Start with small volumes to closely monitor deliverability and address any potential issues.
- Responsible Sending Practices: Gradual increases demonstrate responsible sending practices to ISPs.
- Stable Reputation: Gradual adjustments are preferred for maintaining a stable sending reputation.
- Phase-Out Strategy: Develop a strategy for gradually phasing out the old ESP while increasing volume on the new IP.
Technical article
Documentation from Microsoft shares that you should avoid sudden changes in sending volume. Gradual increases and decreases are preferred to maintain a stable sending reputation and ensure deliverability.
20 Nov 2023 - Microsoft
Technical article
Documentation from Google Postmaster Tools explains to gradually increase sending volume when starting to send email from a new IP address. Starting with small volumes allows you to monitor deliverability and address any issues that arise.
4 Jan 2024 - Google Postmaster Tools
Are IP warming services effective for improving email deliverability?
Can I skip a day during email warm up without hurting my IP reputation?
Do I need an IP warm-up when moving to a new ESP with shared IPs?
Do I need to re-warm my IP after changing the hostname associated with it?
How do I warm up a new IP address for transactional emails?
How do I warm up new IP addresses for email sending?
