A sudden drop in open rate — from 30% to under 10% overnight — is more than alarming. It signals shifts in deliverability, privacy settings, or ISP filtering, all of which can harm your bulk mail, mess mailing, and overall reputation. https://medium.com/@anandbetaitsolution/why-did-my-open-rates-drop-30-this-week-b1fa40c9a6f1