Exchange hybrid mail flow

Question

I have successfully installed and configured exchange 2016 for a hybrid setup in my organization mail flow is up and running for all scenarios except from on-premises to o365. Every other flow works fine. Is there anything I need to do?

Answer 1

Your on-prem Exchange organization must have objects in it that match the mailboxes in Office 365/Exchange Online.

Normally these would be Mail User or Remote Mailbox objects. If there isn't a Mail User or Remote Mailbox object for each cloud mailbox, then on-prem Exchange won't be able to route mail to the cloud.

You can manually create remote mail users in your on-prem organization that match with the cloud mailbox by using the process I outline here: How to reconcile user with both on-premise and cloud mailboxes?

For new mailboxes, the best way to make sure everything works is to create the new mailbox on-prem and then migrate it to the cloud. When you let the mailbox migration wizard migrate it, it automatically creates the correct Remote Mailbox object in your on-prem organization.