I am in the middle of a staged migration from our On Premise Exchange 2010 to Exchange Online. Everything is smooth so far and I successfully started migrating some internal users. However, non migrated users receive an NDR when trying to reach newly migrated users. I found the culprit, which is the autocomplete. Typing the complete address or deleting the autocomplete entry resolve my issue. Is there is any way to force the update dynamically those entries ?