An open event records a request for a remote image. It does not prove that a person read the email, showed interest, or received it in the primary inbox.
An open-tracking event records a request for a remote image. That request alone does not establish that a person read the email.
Apple Mail can preload remote images without recipient action, and security tools can generate non-human activity. Gmail proxies image requests, and Google says senders cannot use image loading to learn about the recipient's computer or location. Images can also be blocked, so a person may read the message without generating an open.
Open data is noisy enough that I would not use it as a prospect-level signal.
Email platforms usually measure opens by inserting a unique, invisible image into the HTML version of a message. When a mail client or another system requests that image, the platform records an open. If the image is not requested, no pixel-based open is recorded. Mailchimp and Twilio SendGrid document the mechanism directly; the UK's Information Commissioner's Office describes tracking pixels as creating a communication between the user's client and a server that can identify when an email was opened.
The image request alone cannot establish whether the recipient read the message or cared about it.
I would not use one reported open to accelerate a follow-up, trigger a sales call, or label a prospect interested.
With Mail Privacy Protection (MPP) enabled, Apple Mail can download remote content in the background whether or not the recipient engages with the message. Apple also routes those requests through relays that obscure the recipient's IP address. Apple tells developers that automatic loading makes the reported viewing time unreliable, and Mailchimp documents the resulting inflation in open reporting. Apple's privacy documentation Apple's developer explanation Mailchimp
MPP can generate an image request without a human view, although settings, filtering, connectivity, and failed requests still affect what gets recorded. Its timestamp, IP address, and location cannot be treated as precise recipient data.
Google's Workspace administrator documentation says Gmail uses Google's secure proxy servers to serve images in messages. Google's Gmail help says senders cannot use image loading to obtain information about the recipient's computer or location, although senders may sometimes know that a message with an image was opened. Google's Gmail help Workspace administrator documentation
Gmail's proxy is not the same as Apple's background loading. Google says senders cannot use the image request to identify the recipient's computer or location. Proxying by itself is not proof of a false open.
Google also says it does not track open rates and cannot verify the accuracy of third-party open-rate data. Its sender guidance warns that a low open rate is not, by itself, reliable evidence of a deliverability problem. Mailchimp separately tells users to evaluate bounces, unsubscribes, and conversions alongside bot-affected engagement metrics. Google Mailchimp
Many email security products inspect messages and links. Mailchimp says antivirus systems, provider security, Apple Mail Privacy Protection, and link-preview generators can open emails or follow links before the contact does. SendGrid reports the same problem and says its own system does not distinguish legitimate from illegitimate clicks because the signal is essentially the same for a human and a bot. Mailchimp SendGrid
Safe Links in Microsoft Defender for Office 365, which applies to organizations licensed for that product, provides a concrete example. It can scan and rewrite URLs during mail flow, verify them at click time, and asynchronously detonate URLs that do not have a valid reputation. That does not mean every security scan becomes a click in every analytics platform. Mailchimp and SendGrid separately document that some security systems do create machine-generated open or click events. Microsoft Mailchimp SendGrid
The same problem affects click reporting. A click can be more useful after known machine activity is filtered, but the raw event is not proof of a human action.
An open pixel requests a remote image. Click tracking changes a destination URL so the recipient passes through a tracking system before reaching the final page. Mailchimp describes adding tracking information to a URL and redirecting the recipient through its servers. SendGrid describes rewriting links and optionally placing the tracking hostname on a customer-controlled domain. Mailchimp SendGrid
Turning off the pixel does not necessarily turn off click tracking. Mailchimp and SendGrid each document open tracking and click tracking as separate settings. The two decisions should be made separately. Mailchimp Mailchimp click tracking SendGrid
Click tracking also adds a hostname and a redirect to the click path. Recipient security products may then apply another layer of rewriting or inspection. Microsoft documents this behavior in Safe Links, and Google's current page says it adds link protection in official Gmail clients and is testing click-time link checks for some third-party email client users. Microsoft Google
Google and Microsoft both document URL evaluation as part of message security. Google tells senders to check the Safe Browsing status of their domains, while Microsoft says Safe Links can detonate URLs that lack valid reputation. Google Microsoft
The tracking hostname becomes another domain that receivers and security products can evaluate. Test its individual effect instead of assuming it helps or hurts placement.
In Google's sender guidelines and Microsoft's Safe Links documentation reviewed for this article, neither provider states that enabling or disabling a tracking pixel has a universal placement effect. No Outlook.com sender-facing page was reviewed for this question. Those sources do not support claims that one pixel always causes spam placement or that disabling open tracking produces a predictable improvement. A custom tracking domain may improve branding and administrative control, but it does not guarantee inbox placement.
If an outbound program wants to test the effect, it should hold the audience, offer, copy, schedule, and sending infrastructure as constant as possible. Measure replies, positive replies, meetings, complaints, and bounces. Comparing reported open rates would test the measurement system, not the business result.
The European Data Protection Board says that distributing tracking pixels or tracking links to a user's device constitutes storage, at least through client-side caching, and that collecting identifiers through them can be considered gaining access under Article 5(3) of the ePrivacy Directive. The ICO says that when email tracking pixels store information on, or access information stored on, a user's device, the UK's PECR storage-and-access rules apply. The compliance analysis depends on the implementation, purpose, jurisdiction, and any applicable exemption. EDPB ICO
This is not legal advice. The practical questions are what the tracking system collects, why it collects it, where the data goes, how long it is retained, and which recipients and jurisdictions are involved.
For outbound operations, we separate these measurements:
An open can remain a lower-confidence diagnostic signal when a real workflow depends on it and the platform filters known machine activity. It should not be used as proof that one prospect read a message, proof that a campaign reached the primary inbox, or the sole reason to accelerate a follow-up.
Our operating recommendation for cold outbound is to leave prospect-level automation based on opens turned off. Keep the pixel only for a documented aggregate use, after reviewing the applicable privacy requirements, and evaluate click tracking separately.
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