Link checkers typically work by scanning the content of your email and extracting the URLs. They then perform a series of checks, including:
HTTP Status Codes: Ensuring that each link returns a 200 OK status and not a 404 Not Found or other error codes. Redirects: Checking if the link redirects to another URL, which could be a sign of phishing or bad user experience. Content Analysis: Some advanced tools also analyze the content of the linked page to ensure it is relevant and appropriate.