What is a custom tracking domain?
A custom tracking domain is a subdomain of yours, such as track.yourdomain.com, that your sending tool uses for its click and open tracking links. You point it at the tool with a CNAME record. Without one, your links use the tool’s shared tracking domain, and its reputation, along with every other customer.
Reading the result
You get the CNAME chain, and the vendor when a hop matches the exact target in that vendor's own setup guide, then the addresses the name resolves to. HTTPS is one request to the domain that follows no redirect: any answer means a TLS connection was made, and a failure shows the reason given. We cannot read the certificate itself. The registered domain is then checked on the domain blacklists we can query.
Beat runs on the same engine, on a schedule, across all 41 checks and 25 blacklists. What it adds is asking again, noticing when an answer changes and telling you what to do about it.
Common problems it finds
The CNAME is proxied through Cloudflare
With Cloudflare's proxy on, public DNS shows Cloudflare's addresses instead of your CNAME, and the sending tool cannot verify the record. Instantly and lemlist both ask for it to be set to DNS only.
No certificate for HTTPS
If the tool writes tracked links as https:// and no certificate covers the name, every click opens a browser warning instead of your page.
The record is on the wrong host
Some DNS panels add the domain to whatever you type as the host, so entering track.yourdomain.com creates track.yourdomain.com.yourdomain.com. The tracking name then resolves nowhere.
A listed link domain
URI blacklists judge the domains in message bodies, so a listed tracking domain puts every message carrying its links at risk, whichever server sends it.