What is “rewrite-from” and why is it used?

Rewrite from is the technique mailing lists use to avoid DMARC failures when subscribers send from domains with strong DMARC policies such as p=reject. The list rewrites the visible From header to its own domain ensuring alignment for SPF and DKIM. This prevents DMARC rejections downstream but comes at a usability cost because replies no longer go to the original author unless Reply To headers are adjusted.