Issue description

Recently install new Exchange 2019 in existing Exchange 2013/2016 org but unable to login to it’s ecp url and getting HTTP ERROR 500.

Cause

This is happenign becasue :

  • Arbitration mailbox is still hosted on Exchange 2013/2016 server
  • And Account used to access ECP does’t have on pre mailbox.
  • Arbitration mailbox is used for anchoring of account without mailbox.

Fix

You can do either of these :

  • Create a local mailbox on Exchange 2019 Database and assign that Org Admin Role
  • Move Arbitration mailbox to Exchange 2019, which you might not feel comfortable until you decide to move your endpoint to new server.

Thank you for reading !