The optimal IP warming strategy, whether ISP-based or volume-based, depends on a multitude of factors. An ISP-based approach provides granular control and can yield excellent results, but it requires more micromanagement. Volume-based warming is generally easier, especially with the improvements in provider reputation tracking. It involves maintaining consistent sending habits, closely monitoring engagement metrics, bounce rates, spam complaints, and sender reputation. Key practices include segmenting recipient lists by engagement level and ISP, prioritizing the most engaged users, adapting strategies to comply with requirements from major ISPs such as Gmail and Microsoft, ensuring the content is high-quality and non-promotional, and maintaining a clean, validated email list. The decision between ISP-based and volume-based often depends on the email list size and quality, and the existing deliverability issues, while avoiding sudden spikes in volume during the warming process is crucial.
18 marketer opinions
The best IP warming strategy, whether ISP-based or volume-based, depends on various factors, including list size, list quality, sending history, deliverability issues, and the level of micromanagement a sender can handle. A granular, ISP-based approach can yield excellent results, while volume-based warming is often easier and effective, especially with improvements in provider reputation tracking. It is a common approach for those with diverse lists. Consistency in sending volume and schedule is crucial, along with close monitoring of engagement metrics, bounce rates, complaint rates, and sender reputation. Segmenting recipient lists by engagement level and ISP, prioritizing engaged users, and adapting to the specific requirements of ISPs like Gmail and Microsoft are also important considerations. High-quality, engaging content and a clean, validated email list are essential for a successful warm-up.
Marketer view
Email marketer from Validity Blog shares the importance of closely monitoring your sending reputation, bounce rates, complaint rates, and blocklist status during IP warming. They say to be prepared to adjust your sending strategy if you see negative indicators.
13 Mar 2024 - Validity Blog
Marketer view
Email marketer from Email Geeks has always done volume based but focused on the ISP. He sends to all ISPs, but the way he does this is he always looks at the ISP with the largest volume and start his volume minimums there. All of the other ISPs with a lesser volume just fall in behind that until you reach full volume required for the client, Gmail is almost always the largest, so he will start at 5000 emails per day per IP address based on the percentage of Gmail addresses in the list and then after three or four days increase volume 1.5×-2x every two days until full volume is reached while monitoring each individual ISP along the way and adjust as needed.
16 Jan 2025 - Email Geeks
3 expert opinions
Experts suggest that the choice between volume-based and ISP-based IP warming strategies depends on several factors. For ease of implementation, volume-based warming can mimic the effects of ISP-based warming through random segmentation, keeping per-ISP levels low. However, the optimal strategy often depends on list size and quality; smaller lists may be sufficiently warmed with a volume-based approach, while larger lists may require a more granular, ISP-focused method. Regardless of the chosen method, a slow and consistent increase in sending volume is crucial to avoid triggering spam filters.
Expert view
Expert from Word to the Wise explains the importance of slowly and consistently increasing sending volume during IP warming. Avoid sudden spikes in volume, which can trigger spam filters.
15 Sep 2021 - Word to the Wise
Expert view
Expert from Email Geeks shares his goal with volume based warming was always to just keep per-ISP levels low enough through random segmentation as to basically keep the effects the same as if you were doing it at a per-ISP level, so he always preferred volume-based because it’s less work and easier segmentation.
17 Sep 2021 - Email Geeks
4 technical articles
Email deliverability documentation emphasizes starting with low sending volumes, especially on new IPs, and gradually increasing over weeks. Close monitoring of bounce rates, feedback loops, and sending reputation is critical. For Gmail, maintain a low spam rate. While there are no specific volume thresholds (Microsoft), consistent sending habits and low complaint rates are vital. Proper reverse DNS configuration is essential to verify IP legitimacy.
Technical article
Documentation from Microsoft Sender Support emphasizes that there aren't specific volume thresholds for IP warming, but shares that consistent sending habits and low complaint rates are key to building a positive reputation. Monitor your sending reputation in the Smart Network Data Services (SNDS).
8 Apr 2024 - Microsoft Sender Support
Technical article
Documentation from RFC-1912 explains the importance of having a properly configured reverse DNS (rDNS) record for your sending IP address. This helps ISPs verify that your IP address is legitimate and not associated with spamming activity.
30 Aug 2023 - RFC-1912
Are IP warming services effective for improving email deliverability?
Do I need an IP warm-up when moving to a new ESP with shared IPs?
Does IP warming require consecutive days of sending or can it be gradual?
How can I automate IP warmup in Iterable?
How do I warm up a new IP address for transactional emails?
How long does it take to warm up an IP address for email marketing?