What’s a broken URL and why does it matter?

A broken URL leads to an error page-typically a 404 (not found) or 500 (server error)-instead of intended content. In email, broken links create two problems: they frustrate recipients who click and find nothing (damaging your brand), and they raise red flags with spam filters that actively verify URL destinations as part of content analysis.

Filters check links for multiple concerning signals: dead endpoints suggesting abandoned or fraudulent campaigns, redirect chains that may obscure final destinations, domains on blocklists for previous malicious activity, and suspicious URL patterns (misspellings of known brands, unusual TLDs, newly registered domains). A legitimate sender should have working links to established domains-broken URLs suggest either incompetence or deception.

Prevention requires pre-send link verification. Most ESPs offer link checking during campaign review. Test every link manually or through automated tools. Be especially careful with dynamic URLs built from personalization or conditional logic-test variations to ensure all paths resolve correctly. A broken link is never just a minor inconvenience; it's a deliverability signal, a user experience failure, and a missed conversion opportunity all in one.