What is a click-tracking and open-tracking domains?

And every Every time your ESP wraps a link in your email, it routes the click through a tracking domain first. When your subscriber clicks, the request hits that tracking domain, registers the event, and instantly redirects to your actual URL. Open tracking works similarly: a tiny invisible pixel image is loaded from a tracking domain when the email renders. These tracking domains are how your ESP gives you click rates, open rates, and individual subscriber activity data.

By default, your ESP uses their own tracking domain. Something like click.mailchimp.com or trk.klaviyo.com. Every link and pixel in your emails points to their infrastructure. That's functional, but it means the domain your subscribers' browsers briefly visit isn't yours. Some spam filters penalize links to shared tracking domains because they're used by thousands of senders with varying reputations. More practically, a shared tracking domain can get flagged when another sender on that same domain behaves badly, and that affects your delivery even though you did nothing wrong.

A custom tracking domain puts your brand's subdomain in the tracking URLs instead. Something like click.yourbrand.com or track.yourbrand.com. You set it up by adding a CNAME record in your DNS pointing to your ESP's tracking infrastructure. Klaviyo, Mailchimp, SendGrid, and most other ESPs support this in their domain settings. The actual click redirect still goes through your ESP's servers, but the URL your subscribers see comes from your domain. This reduces phishing signal risk because the link domain matches (or is related to) your From address.

On open tracking: since Apple Mail Privacy Protection launched in iOS 15, open-tracking pixels are pre-fetched by Apple's proxy servers for Mail app users, inflating open counts significantly. Open rates aren't a reliable primary engagement metric anymore. When you're defining engaged subscribers or setting suppression thresholds, use click-based activity instead of opens.

So if If you want to check whether your tracking domain setup is healthy, Review My Emails can audit the tracking domain configuration in your outgoing emails and flag issues with your CNAME setup or shared-domain reputation. Setting up a custom tracking domain takes about 15 minutes in your ESP's dashboard and is one of the easiest deliverability improvements available to you.