When you set up a custom link tracking domain with Mailtrack, you may expect it to apply to every type of tracking. However, the custom domain only applies to link tracking.
This means that when you insert a tracked link in your email, the link will use your custom domain. Email open tracking and PDF tracking, on the other hand, keep using our standard tracking domain and are not affected by your custom domain configuration.
If you notice that your custom domain appears correctly on tracked links but not on the tracking image used for email opens or on tracked PDF attachments, this is expected behavior and not a configuration issue.
To set up or review your custom domain, see How to set up a custom domain for Mailtrack link tracking.