Summary
IP warming is a critical process for establishing a positive sender reputation with internet service providers (ISPs). Two primary strategies often discussed are ISP-based warming, which involves segmenting sends by major providers like Gmail or Microsoft, and volume-based warming, where the total email volume is gradually increased across all recipients. While ISP-based warming offers granular control and insights into individual provider performance, it typically requires more manual effort and oversight. Volume-based warming, on the other hand, is generally simpler to implement and can be highly effective, especially with diverse, engaged recipient lists.
Key findings
- Granular control: ISP-based warming provides detailed insights into how each major ISP (e.g., Gmail, Microsoft, Yahoo) is receiving your mail, allowing for specific adjustments if issues arise with a particular provider. This can be particularly beneficial for senders with a history of deliverability problems with certain ISPs or those sending large volumes to non-mainstream providers.
- Ease of implementation: Volume-based warming is generally less complex to manage, as it focuses on total send volume rather than segmenting by individual domains. This makes it a popular choice for marketers with limited resources or those prioritizing operational simplicity.
- Provider evolution: Improvements in ISP reputation tracking and inbound deliverability management technology have made volume-based warming more viable and effective than in the past. Major providers are more adept at assessing overall sender behavior.
- Efficiency: While ISP-based warming can accelerate the process for specific providers, the total time to reach full volume might be similar or even longer due to the micromanagement required across multiple segments.
Key considerations
- Audience composition: The choice of strategy can depend on your audience. If a significant portion of your list is concentrated within a few specific, smaller ISPs, a more targeted ISP-based approach might be warranted. For a diverse, organic list, volume-based warming often suffices.
- Resource availability: Implementing an ISP-based strategy demands dedicated personnel for daily monitoring and adjustments. If your team lacks this capacity, a volume-based approach minimizes operational overhead.
- Reputation history: For senders with a history of deliverability issues or those migrating from an ESP with a poor reputation, a more cautious, ISP-based approach (or a hybrid) may be necessary to rebuild trust. Learn more about dedicated IP warm-up best practices.
- Proactive engagement: Regardless of the strategy, maintaining consistent and relevant content, verifying lists, and leveraging feedback loops are crucial for building a positive sender reputation. Explore Twilio's insights on IP warm-up for additional tips. For more on IP warming strategies and volume scaling, read our comprehensive guide.
What email marketers say
Email marketers often weigh the trade-offs between granular control and operational simplicity when choosing an IP warming strategy. Many appreciate the direct oversight that ISP-based warming provides for troubleshooting, while others gravitate towards the lower overhead of a volume-based approach, especially for broad, organic mailing lists.
Key opinions
- Preference for control: Some marketers prefer ISP-based warming due to the enhanced control and visibility it offers, allowing them to monitor performance and address issues with specific domains directly.
- Simplicity wins: Many marketers find volume-based warming to be simpler and less labor-intensive, particularly when managing diverse lists where segmenting by ISP isn't always practical or necessary.
- Adaptive approach: A common sentiment is to start with volume-based warming and only revert to an ISP-specific approach if deliverability issues or blocklists arise for particular providers.
- Hybrid models: Some marketers naturally blend both strategies, focusing on total volume while keeping a close eye on the performance at major ISPs and adjusting as needed, especially for the largest mail streams like Gmail.
Key considerations
- Customer data: The availability of data on customer engagement and audience makeup plays a role in deciding the warming strategy. If you can identify your most engaged users across different ISPs, this can inform your approach.
- Deliverability history: Senders with a past record of deliverability challenges at specific major ISPs should consider a more ISP-focused warming plan or exercise extra caution with those providers initially. This can help mitigate common email deliverability issues.
- Resource allocation: Marketers often lack the time or dedicated resources to perform granular, day-to-day ISP segmentation and adjustments. This practical limitation frequently pushes them towards simpler volume-based methods.
- Avoiding hiccups: If a volume-based warmup is progressing smoothly, it is often advisable to continue with it rather than introducing the complexity of ISP-specific adjustments, unless problems specifically necessitate it. For guidance on IP warming best practices, see Knak's guide.
Marketer view
Marketer from Email Geeks explains their longstanding preference for an ISP-based warming approach. They have segmented by providers like AOL and Gmail for over a decade to gain specific insights into each domain's performance and identify potential issues efficiently.Despite seeing more vendor documentation advocate for volume-based methods, they still lean towards a domain-based strategy. This allows for precise adjustments if deliverability problems arise with a particular ISP, offering a higher degree of control.
Marketer view
Marketer from Email Geeks outlines their strategy for volume-based warming, aiming to maintain low enough per-ISP levels through random segmentation. The goal is to mimic the effects of a per-ISP approach without the added complexity.They prefer this method because it is less work and simplifies the segmentation process. This approach is seen as more efficient for general email sending where deep, granular ISP analysis isn't consistently required.
What the experts say
Deliverability experts acknowledge the merits of both ISP-based and volume-based IP warming strategies. While ISP-based warming offers a higher degree of control and can be beneficial in specific scenarios (e.g., historical deliverability issues with certain ISPs, or for non-major recipients), they often lean towards volume-based warming for its efficiency and ease of management, attributing its success to advancements in ISP reputation systems.
Key opinions
- Effectiveness of both: Experts generally agree that both ISP-based and volume-based warming strategies can yield positive results, depending on the specific context and sender profile.
- Evolving ISP technology: Improvements in how major providers (like Gmail, Yahoo, Microsoft) track and manage sender reputation have made volume-based warming more effective and easier to implement than in previous years.
- Operational overhead: ISP-based warming, while precise, is often described as a slog due to the significant micromanagement required. Volume-based warming is generally preferred for its simplicity.
- Microsoft consideration: Even with volume-based warming, some experts suggest a dedicated focus on Microsoft, potentially breaking them out for separate monitoring or proactive engagement with their sender support teams. For specific advice on why emails fail at Microsoft, check our guide.
Key considerations
- Data sharing limitations: ISPs do not share data on how much mail you send to other providers. This means each ISP evaluates your sending reputation independently, which supports the rationale for ISP-specific monitoring even within a volume-based plan.
- B2B challenges: Implementing a strict per-ISP warming strategy for Business-to-Business (B2B) mail can be particularly difficult without advanced tools, given the diverse range of mail servers involved.
- Consistency is key: Consistent send patterns, with smooth, semi-horizontal magnitude charts, are indicative of good deliverability, regardless of the warming strategy. Spikes in volume can trigger flags. Cisco's Talos Intelligence provides some insights into this. For more, Webbula's guide to IP warming discusses foundational principles.
- Proactive support: Engaging proactively with major ISP sender support teams (e.g., Microsoft's OLC team) by sharing your planned warming schedule can help reduce potential deliverability hiccups. Explore further in our guide on warming up an IP address.
Expert view
Expert from Email Geeks notes that a granular approach, like ISP-based warming, consistently produces excellent results. This method offers detailed insights and control over deliverability performance at each individual provider.However, they also observe that volume-based warming has become increasingly effective due to advancements in provider reputation systems. These systems are more sophisticated than before, simplifying the warming process for senders.
Expert view
Expert from Email Geeks advises that volume-based warm-ups generally work well in their experience. However, they suggest that senders might consider isolating Microsoft for separate attention due to its unique deliverability characteristics.This highlights that while overall volume-based strategies are effective, some major ISPs may still benefit from targeted monitoring or adjustments, indicating a nuanced approach to warming.
What the documentation says
Official documentation from various email service providers and deliverability resources generally emphasizes a gradual increase in send volume as the core principle of IP warming. While some guidelines may touch on ISP-specific considerations, the overarching message points towards a volume-based ramp-up designed to build a consistent and trustworthy sending history.
Key findings
- Gradual ramp-up: The fundamental principle across almost all documentation is to start with a low volume of emails and gradually increase it over time. This controlled sending allows ISPs to observe consistent behavior.
- Time commitment: IP warming is often described as a process that takes several weeks, sometimes 4-6 weeks or more, to establish a good reputation. It requires sustained effort, not a quick burst of activity.
- Focus on engagement: Many resources stress sending to engaged subscribers during warming. High engagement (opens, clicks) and low complaints or unsubscribes are crucial signals to ISPs.
- Consistency: Maintaining consistency in sending patterns, content, and frequency is vital. Erratic sending or sudden spikes in volume can negatively impact sender reputation and lead to emails being blocked or sent to spam.
Key considerations
- Authentication importance: Proper configuration of email authentication records such as SPF, DKIM, and DMARC is a fundamental prerequisite for successful IP warming. ISPs rely on these to verify sender identity. Find out what DMARC, SPF, and DKIM are.
- List segmentation: Segmenting your most engaged customers or best-performing campaigns for the initial warming phases is a common recommendation to send positive signals to ISPs from the start.
- Feedback loops: Leveraging ISP feedback loops (FBLs) is crucial for monitoring complaints during the warming period and promptly removing recipients who mark your emails as spam.
- Avoiding blocklists: Failure to warm IPs correctly can lead to emails being blocked or appearing on blocklists (blacklists). This emphasizes the preventative nature of proper warming. If you are on a blocklist, use a blocklist checker.
Technical article
Documentation from Cordial states that it is essential for marketers to warm their IPs before sending out large volumes of emails. They warn that neglecting this step will likely result in emails being blocked or directed to the spam folder.This highlights the preventative role of IP warming in ensuring deliverability. It serves as a foundational step to avoid immediate negative consequences from ISPs when scaling email campaigns.
Technical article
Documentation from Twilio advises senders to maintain consistency in their email content and relevance as they progressively increase sending volume during IP warm-up. They specifically caution against erratic sending patterns or distributing irrelevant content, as these behaviors can lead to poor deliverability.This emphasizes that the quality and consistency of your email program are just as important as the volume itself. ISPs monitor not only how much you send but also the user reaction to your messages.
Related resources
15 resources
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