How First-Party Open And Click Tracking Works

Email tracking is often described as though it records a simple fact: a person opened a message or clicked a link. In practice, it records requests made by mail clients, security tools and browsers. First-party open and click tracking gives the sender more control over the domain used for those requests, but it does not turn imperfect signals into certainty.

This distinction matters. Used well, tracking can help a permission-based sender understand whether a campaign reached an interested audience, whether links work and where subscribers encounter friction. Used carelessly, it can produce misleading engagement data, privacy problems and links that recipients do not trust.

“First party” has two related meanings in email technology. The common operational meaning is that the tracking pixel and redirect links use a domain or subdomain controlled by the sender, such as links.example.co.uk, rather than a shared platform domain. A stricter meaning is that the sender also operates the collection and redirect service itself. Those are not the same arrangement, and the difference matters for security, contracts and privacy governance.

What first-party tracking means in an email

Most email platforms can record opens and clicks. Without custom configuration, they may insert URLs such as click.vendor-example.net/… and an image source on their own domain. With branded or first-party tracking, the visible host is normally a dedicated subdomain of the sender’s domain:

• links.example.co.uk for click redirects;
• images.example.co.uk or track.example.co.uk for the open pixel;
• occasionally one subdomain for both functions.

The sender delegates that subdomain through DNS to its email service provider or routes it through its own proxy. The email platform can then serve an image or receive a redirect request through a hostname the sender controls. SendGrid, for example, describes link branding as rewriting tracking links and open-tracked images with a customer’s domain instead of its default domain. Its explanation of link branding and SSL click tracking also illustrates why HTTPS must be part of the set-up.

A branded subdomain improves consistency, but it is not automatically a wholly self-hosted tracking system. If links.example.co.uk is a CNAME to an ESP, the provider may still receive, process and retain the event data. That can be perfectly reasonable, provided the sender understands the arrangement and documents the provider’s role. Calling it “first-party” should not obscure where the data actually goes.

How open tracking works

For an HTML email, the sending system adds a tiny remote image, traditionally one pixel by one pixel, to the message body. Its address contains an identifier that associates the request with a particular message and, often, the recipient record. A simplified version looks like this:

<img src="https://track.example.co.uk/o/a8f2…" width="1" height="1" alt="">

When the mail client fetches that remote image, the tracking server records an event. Depending on the configuration, an event record may include the campaign or message ID, recipient or pseudonymous recipient ID, timestamp, request IP address, user-agent string and the tracking hostname. The system can count the first qualifying request as a unique open and later requests as repeat opens.

That is an image request, not direct proof that a human read the message. It can be absent even when a recipient reads the email, because remote images are blocked. It can also be present when the recipient did not read it in the ordinary sense.

Apple’s Mail Privacy Protection is the clearest example. Apple says that, when Protect Mail Activity is enabled, its Mail apps download remote content in the background by default and route it through privacy-preserving relays. This is designed to prevent senders from learning a recipient’s precise Mail activity and IP address. Apple’s Mail Privacy Protection documentation explains the mechanism. An apparent open from an Apple relay can therefore be a content-fetch event rather than evidence of deliberate reading, and IP-derived location should not be treated as reliable.

Other mail clients and corporate security controls may block images, cache them, fetch them more than once or inspect messages before delivery. Open data is consequently useful for broad directional reporting, such as comparing like-for-like campaigns over time, but it is a weak basis for individual-level decisions. Do not treat a non-open as proof that a subscriber is inactive, and do not use opens alone to justify increasing sending pressure.

Why a first-party pixel does not solve the open-rate problem

Using track.example.co.uk instead of a vendor hostname changes the domain the client contacts. It does not change the behaviour of Apple Mail, image-blocking settings, proxy services or security scanners. A first-party pixel may give a more coherent domain footprint and more control over logs, retention and routing, but the basic measurement limitation remains.

How click tracking works

Click tracking works by replacing an original destination URL with a tracking URL. Instead of placing this directly in the email:

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the sending platform places a link resembling this:

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When someone activates the link, the browser makes a request to the tracking endpoint. The endpoint records the event, looks up the approved destination associated with that token and issues an HTTP redirect, usually immediately, to the final page. The browser then loads the destination page.

A well-designed click record can capture the message ID, recipient-level identifier, link ID, destination ID, timestamp and a limited set of request metadata. The token should be opaque: it should not expose an email address, customer number or other personal data in the URL. It should also be hard to guess, expire or become unusable when appropriate, and should only redirect to destinations on an allow-list controlled by the sender.

Click tracking can be used in plain-text messages as well, although the substituted link is more visible. Some links cannot sensibly be tracked through the same mechanism. mailto: links do not create a web request to a redirect service, and anchor links, telephone links, unsubscribe mechanisms and preference-centre links may need special handling. Platform documentation commonly notes these limitations; for example, Mailchimp’s click-tracking guidance explains that only certain HTTP(S) links can be tracked and that system-generated unsubscribe links are handled separately.

One click event is not always one person clicking

Security products routinely inspect links in incoming mail. Microsoft Defender for Office 365’s Safe Links feature can rewrite URLs and scan them before the recipient is directed to the site; in supported Outlook clients it can also perform an additional check at click time. Microsoft’s Safe Links overview describes both URL rewriting and scanning behaviour.

That protection is valuable, but it means a click event can result from a scanner, a prefetcher or another automated process. A forwarded email can create a second problem: the tracking URL may still identify the original recipient even when somebody else uses it. As a result, raw click counts must be filtered and interpreted before they are used in segmentation, attribution or deliverability decisions.

Useful signals for identifying likely automation include several links being requested in seconds, identical timing across many recipients, requests with known scanner user agents, no corresponding page interaction and an unusual sequence such as the unsubscribe link being visited alongside every content link. None is conclusive alone. Filtering should be conservative, auditable and revisited when mailbox-provider behaviour changes.

The role of DNS, TLS and redirect design

First-party tracking is often presented as a branding setting, but it is infrastructure. A fragile configuration can break customer journeys or create a security warning in the inbox.

Use a dedicated subdomain

Use a subdomain rather than the primary website host, for example links.example.co.uk rather than www.example.co.uk. This separates tracking operations from the public website and makes ownership, DNS changes and monitoring clearer. Choose a name that a recipient can recognise without making it overly technical.

A dedicated tracking domain should still be genuinely under the sender’s control. Avoid relying on a domain owned by an agency or a former provider. Domain ownership, DNS access and renewal responsibility should be documented so that a platform migration does not leave old campaign links unusable.

Make every tracking hop HTTPS

The tracking host needs a valid TLS certificate and correct HTTPS behaviour. A click should not downgrade a recipient from a secure email environment into an insecure redirect. Test both the initial tracking URL and the final destination on desktop and mobile clients. SendGrid’s documentation notes that link branding and SSL configuration are separate considerations, which is a useful reminder not to assume a branded hostname is automatically correctly secured.

Prevent open redirects

An open redirect is an endpoint that will send someone to any destination supplied in a URL parameter. Attackers can abuse it to make a malicious link appear to begin on a trusted domain. Tracking services should store approved destinations server-side and redirect by reference to a signed or opaque token, rather than accept a freely supplied url= value.

Keep redirect chains short. A recipient should not pass through a click tracker, an affiliate network, a security wrapper and several analytics services before reaching the intended page. Long chains are slower, harder to debug and less trustworthy when recipients inspect a link.

Plan for old links

Emails can be opened long after their send date. Before changing platforms or DNS, decide how long existing click links must keep working. Keep the old tracking domain and redirect service available for that period, or establish a tested migration path. Removing a CNAME without a redirect plan turns historic emails into dead ends.

Privacy and UK compliance considerations

First-party hosting does not remove privacy obligations. In the UK, email tracking can involve personal data and may also be subject to the Privacy and Electronic Communications Regulations (PECR) rules on cookies and similar technologies. The ICO’s current guidance explicitly includes tracking pixels in email and explains that the fact a technology is first-party or third-party is not the deciding privacy question. The ICO’s guidance on storage and access technologies gives an email-pixel example and says organisations must consider whether the technology stores or accesses information on a user’s device.

This area is fact-specific. The appropriate lawful basis, consent approach and notices depend on what the tracking does, the client technology involved, the audience and other processing. The ICO’s separate direct-marketing guidance also makes clear that compliance for marketing emails does not end with the send itself when pixels are used. Seek specialist legal advice for a programme with material tracking, profiling or international data-transfer implications.

Operationally, responsible senders should:

• explain open and click measurement clearly in privacy information, using language subscribers can understand;
• offer meaningful choices where required and ensure those choices actually affect the relevant tracking;
• collect only the fields needed for the stated purpose;
• set retention periods for granular event data and apply them in systems and exports;
• control access to recipient-level reporting; and
• avoid using inferred location, device details or repeated opens to make intrusive assumptions about people.

For permission-based programmes, click and on-site conversion data are often more useful than attempts to reconstruct a recipient’s reading habits. A subscriber who uses a legitimate preference centre, makes a purchase, downloads a requested resource or returns to the site after a tagged email visit creates clearer evidence of value than an open pixel alone.

Using the data without damaging deliverability

Tracking domains are part of the wider link environment that mailbox providers and recipients encounter. They should align with the brand, be securely configured and point to safe, relevant content. However, a custom tracking domain is not a deliverability shortcut. Authentication, sending behaviour, consent quality, complaint handling, list hygiene and content all remain more fundamental.

There is also a temptation to use raw opens as a suppression rule: send more frequently to people who open, and stop sending to those who do not. That can go wrong in both directions. Apple privacy fetching may falsely promote someone into a high-engagement segment, while image blocking may hide an active reader. Use engagement as a blended, time-bounded assessment that gives more weight to intentional actions, such as verified clicks and conversions, alongside subscription age, stated preferences, recent purchases and complaint or unsubscribe signals.

Where deliverability has deteriorated, it is worth checking whether tracking-domain changes coincided with the problem, whether redirects are secure and whether automated clicks are contaminating engagement logic. That is one of the practical areas a deliverability audit can examine, alongside domain authentication, sending infrastructure and audience suppression rules. It should support a broader diagnosis rather than substitute for one.

A practical example of a sound first-party set-up

A retailer sends a consented monthly product update from news.example.co.uk. It uses links.example.co.uk for click tracking and track.example.co.uk for the open pixel. DNS records delegate those subdomains to its ESP, with valid TLS certificates in place. The platform generates opaque per-message identifiers, records clicks against a fixed list of campaign destinations and sends recipients directly to HTTPS pages on www.example.co.uk.

The retailer labels open data as an estimate, excludes known security-scanner patterns from behavioural automation and uses verified clicks plus on-site events for its most consequential segmentation. It documents the tracking in its privacy material, reviews its provider agreement and deletes granular event logs after its defined retention period. When it changes provider, it preserves the old redirect host long enough for recipients to use links in older messages.

That set-up is less exciting than a dashboard promising precise engagement, but it is more dependable for the sender and more respectful of the recipient.

The central principle

First-party open and click tracking puts the sender’s domain at the centre of the measurement path. Open tracking records a request for remote content; click tracking records a request to a redirect before the destination loads. Both can be useful operational signals, particularly when they are securely implemented, filtered for automation and combined with better evidence of deliberate engagement.

They should never be presented as surveillance-grade facts. A recognisable tracking domain, careful redirect engineering and honest measurement rules produce better reporting than simply collecting more events.

Frequently asked questions

Does a branded tracking domain make tracking first-party?

It makes the tracking hostname sender-controlled, which is the usual operational meaning of first-party tracking. If an ESP operates the endpoint behind that hostname, the provider may still process the data. Check the technical routing and contractual arrangement rather than relying on the label alone.

Are email open rates still reliable?

They are best treated as a directional measure, not a precise count of people who read an email. Image blocking can hide genuine reading, while privacy proxies and automated fetching can create apparent opens without deliberate engagement.

Why do click reports include bot activity?

Corporate security tools and mailbox protections may inspect or scan links to protect recipients from malicious destinations. Those requests can reach a sender’s tracking endpoint and look like clicks unless reporting identifies and filters likely automation.

Can first-party tracking improve inbox placement?

A recognisable, securely configured tracking domain can make links more consistent with the sender’s brand, but it does not by itself improve inbox placement. Consent, authentication, sender reputation, audience quality and complaint rates remain central.

Do UK senders need to consider consent for email tracking pixels?

Potentially. The ICO’s guidance treats tracking pixels as a relevant storage and access technology and explains that first-party versus third-party status is not decisive. The answer depends on the implementation and processing, so organisations should assess their specific use and obtain legal advice where needed.

Sources and further reading

• What are storage and access technologies? — Information Commissioner’s Office
• Mail Privacy Protection & Privacy — Apple
• How to track email opens — Twilio SendGrid
• How to set up SSL click tracking — Twilio SendGrid
• Complete Safe Links overview for Microsoft Defender for Office 365 — Microsoft Learn
• Troubleshooting click tracking — Mailchimp