Migrations from on-premises Exchange to Exchange Online don’t often occur overnight. In many cases, they take weeks or months to complete. During this time, account passwords often change due to password policies, security initiatives, and the like. If the account password changes for the account assigned to a migration endpoint it will cause new migration batches to fail. Unfortunately, the error doesn’t exactly scream “hey, your on-prem password changed for the migration endpoint account.” It’s a bit more ambiguous with the actual error being:

The Mailbox Replication Service was unable to connect to the remote server using the credentials provided. Please check the credentials and try again. The call to ‘https://owa.somedomainsomewhere.com/EWS/mrsproxy.svc’ failed.

NOTE: Don’t get confused by the error indicating “remote server.” Since migrations initiate from Exchange Online, the “remote server” actually is the on-prem server.

Fixing the problem is straight forward. Let’s get to it.

Login to the Exchange Online Admin Center. On the Welcome Dashboard, click Migration under the Recipients heading.

Yes, I use an ocean theme. Don’t judge, I’m a diver after all. Back to the task at hand. When the migration screen opens, a migration job listing appears. Click on the job which received the error.

In the batch details to the right, notice the Associated endpoint. This endpoint is what needs updated with the new password. Click View details next to the endpoint name. The Edit Migration Endpoint window opens. The second textbox displays the Associated administrator displayed. Click Update.

Clicking update allows changing the Associated administrator account and its password. In this case all that needs done is entering the new password, then clicking the Save button.

You’ll see a Please Wait message while the system tests the credentials. If everything passes, the system returns to the Migration Dashboard with your failed batch still selected. Click the start button to resume the migration batch using the new endpoint credentials. Click the Yes button when prompted to resume the migration.

The batch should now complete, but this time without errors!