Summary
Gmail's image proxy significantly impacts the reliability of email open tracking. The proxy caches and downloads images, leading to inflated open rates as Google's servers, not the recipients, trigger the open event. This is compounded by security filters, bots, and Microsoft Defender's 'Safe Links' feature, which pre-fetch images and follow links for security checks, resulting in very fast opens. Additionally, new privacy measures like Apple's Mail Privacy Protection and image caching make open rates a less reliable metric overall. Maintaining a good sender reputation, and implementing SPF/DKIM, are important factors. Emphasis should be put on alternative engagement metrics and the reputation of the tracking domain should be investigated.
Key findings
- Inflated Open Rates: Gmail's image proxy, security filters, and bots inflate open rates, making them an unreliable metric.
- Inaccurate Tracking: Image caching and pre-fetching by proxy servers distort open tracking metrics.
- Fast Opens: Very fast opens are often caused by bots and security systems scanning emails and pre-fetching images.
- Alternative Metrics: Open rates are becoming less reliable due to privacy measures; focus on metrics like clicks and conversions.
Key considerations
- Dedicated IP & Reputation: Using a dedicated IP address and monitoring sender reputation can help manage the impact of image proxying.
- SPF/DKIM Authentication: Proper SPF and DKIM authentication can reduce the likelihood of emails being aggressively scanned.
- Tracking Domain: Investigate the reputation of your click-tracking domain.
- Focus on Clicks: Focus on alternative metrics like click-through rates and conversions to measure email engagement more accurately.
What email marketers say
9 marketer opinions
Gmail's image proxy and security filters significantly impact email open tracking. Gmail's proxy downloads images before the recipient opens the email, inflating open rates and making pixel-based tracking unreliable. Additionally, security filters and bots often pre-fetch images and follow links for security checks, leading to very fast opens. New privacy measures such as Apple's Mail Privacy Protection and image caching mean that open rates are becoming a less reliable metric.
Key opinions
- Inflated Open Rates: Gmail's image proxy downloads images before the recipient views the email, inflating open rates.
- Unreliable Tracking: Image proxying makes open tracking less reliable as the proxy server, not the actual recipient, triggers the open event.
- Security Scans: Security filters and bots pre-fetch images and follow links to scan for malicious content, causing very fast opens.
- Impact of New Privacy Measures: New privacy measures make open rates a less reliable metric. Focus on alternative metrics, like clicks and conversions.
Key considerations
- Dedicated IP: Using a dedicated IP address and monitoring sender reputation may help mitigate the impact of image proxying.
- Alternative Metrics: Focus on alternative metrics like click-through rates and conversions to measure email engagement more accurately.
- Email Scanning: Be aware that bots scanning your emails contribute to inflated numbers - this can be tested by running seed lists with bot detection software.
Marketer view
Email marketer from SparkPost shares that security filters and bots will follow links, including image links in emails, to evaluate the safety of the URL, triggering opens very shortly after delivery.
24 Jan 2025 - SparkPost
Marketer view
Email marketer from Reddit shares that Gmail's image proxy makes open tracking unreliable, resulting in skewed and inflated open rates because images are loaded by Google's servers before the recipient views the email.
21 Jul 2022 - Reddit
What the experts say
4 expert opinions
Gmail's image proxy significantly impacts email open tracking. The Google proxy obfuscates IP addresses and caches images, leading to inflated open rates since images are downloaded by Google's servers, not necessarily the recipients. This makes open tracking inaccurate. Furthermore, automated bot clicks and scans from security systems can cause very fast opens, artificially inflating open rates. Investigating the click tracking domain's reputation is also important.
Key opinions
- IP Obfuscation: Google's proxy hides the recipient's IP address.
- Inflated Open Rates: Image caching by Gmail's proxy leads to skewed open rates.
- Automated Bot Clicks: Automated bots and security scans inflate open rates with very fast opens.
- Link Following: Security filters follow links to evaluate the safety of the URL, triggering early opens.
Key considerations
- Tracking Domain Reputation: Investigate the reputation of the click tracking domain.
- Security System Impact: Factor in the impact of security systems and bots on open rate metrics.
Expert view
Expert from Email Geeks explains that the Google proxy obfuscates the recipient's IP address and may only show the initial read. She suggests that the recorded opens may be legitimate and caused by filters following links to determine URL safety.
18 Oct 2023 - Email Geeks
Expert view
Expert from Wordtothewise.com shares that automated bot clicks and scans from security systems can cause very fast opens, artificially inflating open rates and distorting engagement metrics.
25 Aug 2021 - Wordtothewise.com
What the documentation says
4 technical articles
Gmail's image proxy significantly impacts email open tracking. Gmail caches images to improve user experience, leading to multiple recorded opens even without the user re-opening the email. Litmus explains that Gmail's proxy distorts open tracking metrics. Additionally, Microsoft Defender's 'Safe Links' scans URLs, pre-fetching images and resulting in early opens. RFC documentation suggests that proper SPF and DKIM authentication can reduce the likelihood of aggressive pre-fetch scans, improving deliverability.
Key findings
- Image Caching: Gmail caches images, inflating open rates and potentially recording multiple opens for a single email.
- Distorted Metrics: Gmail's proxy distorts open tracking metrics, making open rates an unreliable indicator of engagement.
- Safe Links: Microsoft Defender's 'Safe Links' feature pre-fetches images, contributing to early opens.
- SPF/DKIM Impact: Proper SPF and DKIM authentication can reduce aggressive pre-fetch scans.
Key considerations
- Authentication: Implement robust SPF and DKIM authentication to improve email deliverability and potentially reduce pre-fetch scans.
- Alternative Metrics: Acknowledge the limitations of open rates as a metric and consider alternative metrics like click-through rates and conversions.
- Scanning Impact: Recognize that automated scanning processes from security software impact open metrics, making interpretation more complex.
Technical article
Documentation from Litmus explains that Gmail uses a proxy to load images. This leads to inflated open rates as the proxy server loads the images instead of the actual recipient, therefore distorting open tracking metrics.
5 Jul 2021 - Litmus
Technical article
Documentation from RFC explains that proper SPF and DKIM authentication can reduce the likelihood of emails being flagged and scanned rapidly, as ISPs trust authenticated emails more, reducing the need for aggressive pre-fetch scans.
26 Apr 2025 - RFC-Editor
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