Optimizely change history: Email Campaign Delivery Drops — NA Region

Optimizely reported a major degradation dropping some email campaign messages in the NA Region from 2026-06-17 14:00 UTC to 2026-06-20 17:41 UTC, lasting 3 days 3 h. Optimizely cited a likely SendGrid header-processing incompatibility and deployed a fix; it lacked records identifying which recipients received messages, complicating decisions about rerunning affected campaigns.