# Deliverability horror stories: what actually broke inbox placement
Canonical: https://inboxdigest.io/ja/posts/deliverability-horror-stories

Three recent client fires: shared sending domain with marketing and transactional mail, DMARC p=none left in place for two years, and a list reactivation blast to cold contacts after switching ESPs.

None of these are AI-specific. All three clients asked whether a new AI ESP would fix deliverability. No. Authentication, list hygiene, and sending patterns fix deliverability.

Useful references: Gmail sender guidelines and Yahoo sender requirements. M3AAWG docs for the long read.