Maildoso includes a built-in Global Custom Domain Tracking option that we handle on our side, and it's turned on by default for your account — so you don't need to set up a custom tracking domain in your sending tool.
Where to find the setting
Click your profile icon in the top-right corner and open Settings.
On the General tab, the Global Custom Domain Tracking toggle is at the top (leave it on for the best deliverability).
Why you can't add your tool's own tracking domain
Because we fully manage your domain's DNS, we don't support adding a third-party / custom tracking CNAME from your sending tool (Instantly, Smartlead, lemlist, etc.). Sending still works normally — only the tool's own custom open/click tracking domain can't be verified on a Maildoso-managed domain. Our built-in tracking covers link tracking for you.
For what the built-in tracking is and how it works, see What's a Global Custom Tracking Domain?