Summary
When assessing email deliverability, Unique Open Rate (UOR) is generally considered the more critical metric. While Total Open Rate (TOR) counts all opens, UOR specifically measures how many distinct recipients opened an email, making it a truer indicator of audience engagement and a direct signal for Internet Service Providers (ISPs) regarding sender reputation and inbox placement. This focus on unique engagement helps ISPs gauge the relevance and trustworthiness of your sending practices. However, it is increasingly important to acknowledge that privacy features, such as Apple's Mail Privacy Protection, can significantly impact the accuracy of all open rates, potentially inflating or fabricating them. In light of these changes, a holistic approach that includes other engagement metrics like clicks and conversions is often recommended for a more comprehensive understanding of email performance.
Key findings
- UOR is Preferred for Deliverability: The overwhelming consensus among email marketing experts and leading documentation from Email Service Providers (ESPs) is that Unique Open Rate (UOR) is the superior metric for assessing email deliverability, as opposed to Total Open Rate (TOR).
- ISP Signal for Sender Reputation: UOR directly reflects the number of distinct individuals engaging with your emails, which is a crucial signal for Internet Service Providers (ISPs). A consistent and healthy UOR indicates positive sender reputation and influences inbox placement, as ISPs prioritize relevance and trustworthiness based on unique user interaction.
- TOR's Limitations: Total Open Rate (TOR), which counts every open including multiple opens by the same recipient, can be misleading. It may inflate engagement numbers and obscure the true reach of a campaign, as a few highly engaged individuals can skew the overall metric, making it less useful for a precise deliverability assessment.
- UOR Reflects True Audience Reach: UOR provides a clearer and more accurate picture of how many unique subscribers are actually interacting with your emails. This insight into unique audience engagement is vital for understanding list health and the breadth of your campaign's reach.
Key considerations
- Impact of Mail Privacy Protection: It is crucial to consider that privacy features like Apple's Mail Privacy Protection (MPP) can significantly inflate or fake open rates, rendering both Unique Open Rate (UOR) and Total Open Rate (TOR) less reliable for assessing actual engagement or inbox placement. In such cases, marketers are advised to prioritize other metrics.
- Conversion vs. Deliverability Metrics: While conversion rate is a vital metric for overall marketing campaign success, it primarily reflects content effectiveness and is not directly tied to deliverability. Unique Open Rate, however, specifically addresses deliverability and the pre-open experience, making it the more relevant metric for inbox placement assessments, even if conversion rates are low.
- Holistic Metric Analysis: Given the unreliability of open rates due to privacy changes, a comprehensive assessment of email deliverability should also incorporate other key engagement metrics such as clicks, conversions, bounce rates, spam complaints, and unsubscribes to gain a more accurate understanding of audience interaction and sender reputation.
- Dataset Analysis: For specific campaigns or sending patterns, analyzing a large dataset can provide insights into the relationship between TOR and UOR, helping to understand audience behavior and potential impacts on deliverability.
What email marketers say
10 marketer opinions
Building on the understanding that Unique Open Rate (UOR) is a crucial metric for deliverability, it's essential to recognize its role in demonstrating genuine subscriber engagement to Internet Service Providers (ISPs). Unlike Total Open Rate (TOR), which merely tallies every instance an email is opened, UOR focuses on distinct individuals, providing a clearer picture of actual reach and audience interest. This unique engagement signal is paramount for sender reputation, as ISPs interpret consistent UOR as a strong indicator of relevant and trustworthy communication, influencing inbox placement more directly than the cumulative, potentially inflated, figures seen in TOR.
Key opinions
- UOR for True Engagement: Unique Open Rate is the definitive metric for gauging how many individual subscribers are truly interacting with emails. This directly reflects list health and the broadness of campaign reach, which are critical for deliverability.
- ISP's Preference: Internet Service Providers prioritize Unique Open Rate as a key signal for sender trustworthiness and content relevance. They use the number of distinct opens to determine inbox placement, favoring senders who demonstrate consistent unique engagement.
- TOR's Deliverability Irrelevance: Total Open Rate is less valuable for deliverability assessment because it can be misleadingly high due to a small number of highly active subscribers opening an email multiple times. This metric does not accurately represent the overall health of an email list or its engagement across unique recipients.
- Deliverability vs. Content: While conversion rates speak to content effectiveness, Unique Open Rate specifically assesses deliverability and the pre-open user experience. A strong UOR indicates successful inboxing, even if conversion rates might be low due to other factors.
Key considerations
- Open Rate Accuracy Challenges: It's important to remember that all open rates, including UOR and TOR, face increasing inaccuracies due to privacy features like Apple's Mail Privacy Protection. These features can artificially inflate open numbers, making it vital to supplement analysis with other engagement metrics.
- Holistic Deliverability View: Relying solely on open rates, even UOR, is insufficient for a comprehensive deliverability assessment. Marketers should analyze a range of metrics, including click-through rates, conversions, bounces, complaints, and unsubscribes, to form a complete picture of email performance and sender reputation.
- Understanding Metric Differences: For effective deliverability management, it's crucial to understand the distinct purposes of UOR and TOR. UOR provides insights into individual reach and ISP perception, while TOR can offer a secondary view into overall engagement intensity from those who have already opened.
Marketer view
Email marketer from Email Geeks explains that Conversion Rate is the most important metric for marketing campaigns, suggesting that opens are an unreliable metric due to email client configurations. He notes that if conversions are low, it could indicate a marketing message issue or a deliverability problem, with increases in bounces, complaints, and unsubscribes hinting at deliverability issues. He also states that Unique Open Rate (UOR) is an acceptable metric, despite its increasing inaccuracy.
22 Sep 2022 - Email Geeks
Marketer view
Email marketer from Email Geeks explains that Conversion Rate measures content effectiveness, while Unique Open Rate (UOR) speaks to both deliverability and the effectiveness of the pre-open experience. She clarifies that a good UOR (e.g., 20%) can indicate no spam placement problem, even if conversion rates are low. She emphasizes that UOR is less inaccurate than Total Open Rate (TOR) because it accounts for multiple opens or device usage, suggesting that the same inaccuracies apply to all senders. She also recommends analyzing a large dataset to understand the relationship between TOR and UOR.
17 Jun 2024 - Email Geeks
What the experts say
1 expert opinions
In light of evolving privacy protections, open rate metrics, whether Unique Open Rate (UOR) or Total Open Rate (TOR), are no longer reliable indicators for assessing email deliverability. Features like Apple's Mail Privacy Protection (MPP) and other email client pre-fetching services frequently inflate or fabricate open events. This makes these traditional metrics largely meaningless for gauging genuine subscriber engagement or confirming successful inbox placement. Instead, email marketers should prioritize more dependable performance indicators.
Key opinions
- Open Rates Unreliable: Neither Unique Open Rate nor Total Open Rate reliably assesses email deliverability anymore.
- Artificial Inflation: Email client privacy features, including Apple's Mail Privacy Protection and pre-fetching, artificially inflate or fake open counts.
- No Indicator of Engagement: Due to these changes, open rates are no longer meaningful for gauging actual subscriber engagement or confirming inbox placement.
- Focus on Action Metrics: Marketers are advised to shift their focus to more dependable metrics, such as clicks, conversions, and subscriber acquisition or retention, for true performance assessment.
Key considerations
- Re-evaluating Open Rates: The utility of open rates as a primary deliverability metric has been significantly diminished, necessitating a re-evaluation of their role in reporting.
- Impact of Privacy Features: Understand how features like Apple's Mail Privacy Protection fundamentally alter the accuracy of open rate data.
- Shift to Engagement Metrics: Prioritize metrics that reflect explicit user actions, such as clicks and conversions, as more accurate indicators of deliverability and campaign success.
- Holistic Deliverability Assessment: Develop a comprehensive deliverability assessment strategy that moves beyond open rates to include more reliable engagement and acquisition data.
Expert view
Expert from Word to the Wise explains that open rates, including both Unique Open Rate (UOR) and Total Open Rate (TOR), are no longer reliable metrics for assessing email deliverability. Due to privacy features like Apple's Mail Privacy Protection (MPP) and other email client pre-fetching, opens are often inflated or faked, rendering these metrics meaningless for gauging actual engagement or inbox placement. Marketers are advised to focus on more dependable metrics such as clicks, conversions, and subscriber acquisition/retention.
22 Jun 2024 - Word to the Wise
What the documentation says
5 technical articles
Historically, and according to leading email service providers and experts, the Unique Open Rate (UOR) has been the preferred metric for assessing email deliverability. This is because UOR accurately measures how many distinct individuals opened an email, providing a truer picture of audience engagement and serving as a vital signal to Internet Service Providers, ISPs, about sender reputation. While Total Open Rate (TOR) counts all opens, even multiple ones from the same recipient, it can inflate figures and obscure actual reach, making it less useful for genuine deliverability insights. However, it's crucial to acknowledge the evolving landscape where privacy features significantly compromise the accuracy of all open rates, prompting a shift toward other reliable engagement metrics for a comprehensive deliverability assessment.
Key findings
- UOR for Unique Engagement: Unique Open Rate (UOR) is consistently cited as the superior metric for deliverability because it counts individual subscribers who open an email, reflecting true audience reach and engagement, unlike Total Open Rate (TOR).
- ISP Signal: Major Email Service Providers, ESPs, confirm that UOR provides a direct and more accurate signal to Internet Service Providers, ISPs, about a sender's reputation and the relevance of their content, influencing inbox placement.
- TOR's Limitations: Total Open Rate (TOR) is less effective for deliverability assessment as it can be skewed by repeat opens from a few individuals, obscuring the actual number of unique engaged subscribers and the true breadth of a campaign's reach.
Key considerations
- Historical Context vs. Current Reality: While Unique Open Rate (UOR) was historically the preferred deliverability metric, it's essential to understand that modern privacy features now significantly impact the accuracy of all open rates, making them less reliable for true deliverability insights.
- Beyond Open Rates: Given the diminished reliability of open rates, a robust deliverability assessment strategy must pivot to other metrics such as click-through rates, conversions, and direct subscriber feedback, for example, unsubscribes, spam complaints.
- Understanding Metric Purpose: Differentiating between UOR for unique engagement and Total Open Rate (TOR) for overall activity intensity, among openers, remains important. However, neither should be solely relied upon for deliverability in the current privacy landscape.
Technical article
Documentation from Litmus explains that while Total Open Rate (TOR) tracks all opens (including multiple opens by the same recipient), Unique Open Rate (UOR) counts each subscriber only once, regardless of how many times they opened the email. For deliverability assessment and understanding audience engagement, UOR is generally preferred as it gives a truer picture of how many individual subscribers are interacting with your emails, which is a key signal for ISPs.
30 Dec 2021 - Litmus
Technical article
Documentation from SendGrid states that Unique Open Rate (UOR) is a more accurate metric for understanding how many distinct recipients opened your email, making it better for assessing overall audience engagement and, by extension, deliverability performance. Total Opens, while showing overall activity, can be skewed by a few highly engaged individuals, obscuring the true reach of your campaign.
7 Nov 2023 - SendGrid Documentation
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