Summary
While a minor, temporary dip or fluctuation in Sender Score might occur early in the IP warming process as a new IP establishes its reputation, a significant or sustained drop is widely considered a concern for email deliverability. This decline often signals that the warming strategy is encountering issues, such as sending too much too quickly, targeting unengaged recipients, or generating high bounce rates and spam complaints, thereby accumulating negative reputation rather than positive. Major ESPs and many experts emphasize that the primary goal of IP warming is to build trust, and a falling Sender Score indicates that negative signals are outweighing positive ones, requiring immediate investigation and adjustment to sending practices. However, some professionals advise against relying solely on Sender Score, highlighting its limitations as a 'porthole view' and encouraging a greater focus on organic engagement data like opens, clicks, unsubscribes, and spam complaints for a comprehensive understanding of deliverability performance.
Key findings
- General Concern: Most email experts and major Email Service Providers (ESPs) agree that a significant or sustained drop in Sender Score during IP warming is a red flag, indicating that the process is not successfully building a positive reputation for the new IP.
- Underlying Issues: Such reputation declines often point to fundamental problems, including sending too much email too quickly, targeting unengaged recipients, hitting spam traps, experiencing high bounce rates, or incurring increased spam complaints, all of which actively undermine the warming process.
- Action Required: When a noticeable drop in Sender Score occurs, immediate investigation and adjustment of sending practices are crucial. This includes slowing down sending volume, refining list quality, and focusing on highly engaged subscribers to mitigate long-term deliverability damage and prevent the IP from accumulating a negative history.
- Limited Metric: Some deliverability professionals caution that Sender Score is a 'limited data point' or 'guide at best' rather than a definitive measure of deliverability across all Internet Service Providers (ISPs), recommending that email marketers prioritize monitoring their own organic engagement metrics.
Key considerations
- Monitor Organic Metrics: Always cross-reference Sender Score changes with your own organic data, such as open rates, click-through rates, and especially negative feedback like unsubscribe rates and spam complaints, for a comprehensive view of reputation during IP warming and beyond.
- Identify Root Causes: If Sender Score drops, actively investigate the potential reasons, which might include aggressive sending volumes, poor list hygiene, or content issues, rather than just observing the score in isolation.
- Adjust Warming Strategy: Be prepared to modify your IP warming plan immediately upon detecting a concerning drop. This may involve reducing sending volume, segmenting for highly engaged users, or cleaning your lists to reverse negative trends and protect deliverability.
What email marketers say
11 marketer opinions
The consensus among email marketing experts is that a sustained or significant drop in Sender Score during IP warming is a definite cause for concern, despite the understanding that minor, temporary fluctuations may occur. Such a decline indicates that the new IP is not successfully establishing a positive sending reputation; rather, it is acquiring negative signals. This typically points to fundamental issues within the warming strategy, such as sending too many emails too quickly, targeting unengaged or poor-quality lists, or experiencing elevated rates of spam complaints and bounces. While some professionals highlight Sender Score's limitations, viewing it as 'a guide at best' rather than a complete picture, a consistent downward trend serves as a critical warning that negative interactions are outweighing positive ones, necessitating immediate re-evaluation and adjustment of sending practices to safeguard future deliverability.
Key opinions
- Reputation Decline: A persistent drop in Sender Score signals that the new IP is accumulating negative reputation, directly undermining the goal of IP warming to build trust with Internet Service Providers (ISPs).
- Strategy Flaws: This decline often points to critical issues in the IP warming strategy itself, including an overly rapid increase in sending volume, inadequate list segmentation, or a failure to focus on highly engaged subscribers.
- Negative Feedback: It is typically a symptom of increased negative feedback from recipients, such as higher spam complaint rates, elevated unsubscribe rates, or an uptick in hard bounces, all of which damage sender reputation.
- Warning Metric: Though acknowledged as a limited metric, a consistent drop in Sender Score acts as an essential early warning system, prompting the need for deeper investigation and strategic adjustments beyond just the score itself.
Key considerations
- Prioritize Organic Data: While observing Sender Score, always prioritize analyzing your own organic engagement metrics, including opens, clicks, and negative feedback signals, as these provide a more comprehensive view of deliverability health.
- Immediate Re-evaluation: Upon noticing a sustained drop, immediately re-evaluate and adjust your IP warming strategy by potentially slowing down send volume, re-segmenting your audience to engaged users, or cleaning your email lists.
- Proactive Problem Solving: Do not wait for a complete collapse in deliverability. Act proactively to identify and address the root causes of the Sender Score decline, as early intervention can prevent long-term damage to your sending reputation.
Marketer view
Email marketer from Email Geeks explains that organic data should be trusted over Sender Score, advising to monitor changes in organic stats like opens and negative engagements (unsubscribes, spam complaints) as Sender Score is a limited, not a full-picture assessment.
7 Oct 2022 - Email Geeks
Marketer view
Email marketer from Email Geeks responds that a drop in Sender Score alone isn't cause for immediate alarm; it's a limited data point, a 'porthole view' that doesn't see everything, and suggests watching for other measurable problems and potential issues at smaller, unmeasurable ISPs, advising it's not enough on its own to confirm something is wrong.
10 May 2024 - Email Geeks
What the experts say
3 expert opinions
A decline in Sender Score during IP warming, particularly when integrating new IP addresses, is not always an immediate cause for alarm, but it certainly warrants careful attention. Experts suggest that while new IPs naturally start with lower scores and may experience minor fluctuations as they establish their sending patterns and reputation, a dramatic or sustained drop is a clear red flag. The key lies in distinguishing between typical warming fluctuations and genuine deliverability issues. Therefore, monitoring Sender Score must be complemented by a close watch on other critical metrics, such as bounce rates and spam complaints, to understand the full picture of an IP's reputation building.
Key opinions
- Initial Fluctuation: During IP warming, especially with new IP addresses, a naturally low initial Sender Score and subsequent minor fluctuations are common as the IP builds its sending history.
- Dramatic Drop Warning: While small dips are normal, a dramatic or significant drop in Sender Score at any stage, including warming, signals potential underlying deliverability problems that require immediate investigation.
- Monitor Other Metrics: Sender Score should not be the sole indicator of deliverability health; close monitoring of critical metrics like bounce rates, complaint rates, and engagement data is essential.
- Reputation Reflection: Sender Score reflects an IP's sending reputation, and a dip during warming can occur as a new IP establishes its trust with ISPs, requiring careful oversight to ensure positive trajectory.
Key considerations
- Contextualize Score: Assess Sender Score drops within the context of your IP warming phase, differentiating between normal, minor fluctuations common to new IPs and more severe, sustained declines.
- Holistic Data Review: Always cross-reference Sender Score changes with your own internal data, including open rates, click-through rates, and especially negative feedback like unsubscribes and spam complaints, for a comprehensive understanding.
- Investigate Promptly: If a significant drop occurs, promptly investigate the root causes, such as overly aggressive sending volume or list quality issues, to address potential deliverability problems before they worsen.
- Adapt Strategy: Be prepared to adjust your IP warming strategy if negative trends emerge, which might include slowing down sending, refining list segments, or cleaning recipient lists.
Expert view
Expert from Email Geeks questions the current data sources feeding Validity for Sender Score.
12 Sep 2022 - Email Geeks
Expert view
Expert from Spam Resource explains that a drop in Sender Score during IP warming, particularly when introducing new IPs, is not necessarily a cause for panic, but warrants close attention. He advises that Sender Score reflects reputation, and as new IPs establish their sending patterns, fluctuations, including a dip, can occur. The key is to monitor other crucial metrics like bounces and complaints and to investigate the underlying reasons for the drop, distinguishing between normal warming fluctuations and genuine deliverability issues.
17 Dec 2024 - Spam Resource
What the documentation says
5 technical articles
During the crucial process of IP warming, where the aim is to establish a positive sender reputation, any decline in metrics like Sender Score is widely regarded as a significant concern for email deliverability. Leading email platforms and deliverability experts emphasize that while minor fluctuations might occur, a sustained or significant drop suggests the warming strategy is generating negative signals, such as high bounce rates, spam complaints, or sending to disengaged audiences, rather than building trust. Such a trend necessitates immediate investigation and adjustment to prevent long-term damage to inbox placement.
Key findings
- Signifies Issues: A drop in Sender Score during IP warming is consistently viewed as a red flag, indicating that the warming process is encountering issues rather than successfully building a positive reputation.
- Strategy Flaws: This decline often points to fundamental problems in the warming strategy itself, such as sending too rapidly, targeting unengaged recipients, or inadvertently hitting spam traps.
- Negative Signal Accumulation: Instead of establishing trust, a falling score suggests the IP is accumulating negative signals, including high bounce rates, increased spam complaints, or sending to poor-quality lists.
- Immediate Action Required: Experts across the board agree that a noticeable drop in Sender Score demands prompt investigation and adjustment to sending practices to prevent long-term deliverability damage.
Key considerations
- Probe for Causes: Immediately investigate the underlying reasons for any significant Sender Score decline, focusing on factors like sending volume, list quality, content, and recipient engagement levels.
- Adapt Warming Plan: Be prepared to modify your IP warming strategy and schedule, which may involve reducing sending volume, refining audience segmentation, or cleaning your email lists to reverse negative trends.
- Focus on Engagement: Prioritize sending emails to your most engaged subscribers during the warming phase to generate positive signals and reinforce a healthy sender reputation.
- Holistic Monitoring: While Sender Score is important, always cross-reference it with other crucial metrics like bounce rates, spam complaint rates, and engagement data for a complete picture of your deliverability health.
Technical article
Documentation from Validity explains that a drop in Sender Score during IP warming can be a concern, as the goal is to build a positive reputation. While minor fluctuations might occur as data aggregates, a significant or sustained drop indicates an issue with the warming strategy, such as sending too fast, to unengaged recipients, or hitting spam traps, requiring immediate investigation and adjustment.
19 Aug 2024 - Validity (formerly Return Path)
Technical article
Documentation from Twilio SendGrid shares that while IP warming is a delicate process of building trust, a significant drop in reputation metrics, including Sender Score, is generally a red flag. It indicates that the sending practices (volume, list quality, engagement) are not aligned with building a positive reputation, and immediate adjustments are necessary to prevent long-term deliverability issues.
10 Jun 2025 - Twilio SendGrid Documentation
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