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

Public URL shorteners (bit.ly, tinyurl) are risky for email because spammers abuse them heavily. Spam filters have learned to treat them with suspicion. Your legitimate link shares reputation with every spammer who uses the same service.

Safe alternatives: Your own branded short domain (links.yourbrand.com). ESP's tracking domains-properly configured with good reputation. Full destination URLs-often fine; the shortener adds no value for email.

Control your link reputation. When you use a shared shortener, you're trusting that no one else has poisoned that domain with spam. With your own domain or your ESP's managed links, you control the reputation. The minor URL brevity benefit of public shorteners isn't worth the deliverability risk.