What are “safe” vs “unsafe” URL shorteners?

You've built a promotional email with four tracked links. Before you hit send, consider where those links are actually pointing. A standard bit.ly shortener might seem harmless, but spam filters don't see it that way. The domain doing the shortening matters just as much as the destination URL.

"Unsafe" URL shorteners in email are shared public services where anyone can create links: bit.ly, tinyurl.com, and similar tools. Because spammers abuse these services constantly, they frequently appear on domain block lists. When your email contains a bit.ly link, spam filters see a domain associated with spam activity, not your sending domain. It doesn't matter that your specific link points to a legitimate product page. The shortener's shared reputation is the problem.

"Safe" URL shorteners are either your ESP's properly configured tracking domain or your own branded subdomain. When you enable click tracking in Klaviyo, Mailchimp, or any major ESP, it rewrites your links through a tracking domain (often something like click.youresp.com). These are safer because they're tied to a reputation the ESP actively manages. Branded tracking domains (your own subdomain, like links.yourcompany.com) are safer still because spam filters can evaluate them against your established sending history.

The practical rule: don't use public URL shorteners in email. Use the built-in click tracking your ESP provides, and if your ESP supports it, configure a custom tracking domain on your own subdomain. If you're not sure whether your current tracking setup uses a shared or branded domain, check your ESP's domain settings or look at the actual rewritten URL in a test send. A shared ESP subdomain is better than bit.ly, but your own subdomain is better than both.