Object reference not set to an instance of an object error and message trace fails in an Exchange hybrid environment

Original KB number:   4481099

Symptoms

Considering this scenario:

• You're working in a Microsoft Exchange Server hybrid environment.
• A message is sent from an on-premises mailbox to an Exchange Online mailbox.
• You try to trace the message in Delivery Reports in the on-premises Exchange organization.

In this scenario, the trace fails, and you receive this error message:

Object reference not set to an instance of an object.

Cause

This is by design. Exchange Server does not support tracing a message that's sent from on-premises to the cloud in a hybrid environment.

Workaround

To work around this problem, run the message trace from Microsoft 365 to get a partial trace on the cloud side. Be aware that this does not show the on-premises path.