When click tracking is enabled, every link in your email gets rewritten to pass through a redirect domain that records the click before forwarding the reader on. The question is whose domain does that job.
The default is a shared domain
Out of the box, most ESPs route tracking through a domain shared across many customers. Shared domain, shared reputation: if other senders on it behave badly, the domain’s standing degrades—and every link in your email now carries that smell. You did nothing wrong and inherited the damage anyway, which should sound familiar if you’ve read the dedicated IP answer. Links are the same story with worse defaults.
Why your own domain wins
- Link alignment. Inbox providers like consistency between the sending domain and the domains inside the message. Tracking links on
links.yourdomain.comalign; tracking links on a third-party domain are a small, persistent mismatch. - Reader trust. Hover over a link and the URL shown is yours, not an unfamiliar redirect host. Recipients trained to distrust weird domains have one less reason to hesitate—and so do the filters that think like them.
- Isolation. Your tracking reputation rides on your behavior alone, like everything else on your domain should.
The setup
It’s one DNS record. On Resend, custom tracking domains are free: pick a tracking subdomain (say, links.yourdomain.com) in the domain’s configuration, add the record, and all tracking routes through it automatically—configurable via the API too. Both open and click tracking are off by default, so this only matters once you switch something on.
The verdict logic
The qualifier carries the whole answer: this is a yes precisely when tracking is enabled. If you track nothing—a reasonable choice for transactional mail—there are no tracking links to align and nothing to set up. But the moment tracking is on, running it through someone else’s domain is an unforced error.