Exchange Server 2019 mrsProxy 401 UnAuthorized Error (Trying to Migrate to Exchange Online)

Question

Hello, 

 

I am trying to migrate from an exchange server 2019 on prem server to exchange online. However I keep getting the 401 unauthorized error. I get it at every point. If i do HCW i get it, test migration availability, setup migration endpoint in m365. Also to note I am using Mimecast as my email gateway. Also get same error from BitTitan's MigrationWiz. 

 

Settings that are set:

MRS Proxy Enabled

Basic / Windows authentication Enabled

Credentials are correct for accounts

Enhanced Protection Disabled

Account has Organization Management and Impersonation.

 

Here is the error i get with the Hybrid Configuration Wizard. Similar error received when doing other migration attemtpts. 

"HCW8078 - Migration Endpoint could not be created. Microsoft.Exchange.Net.CommunicationErrorTransientException The call to 'net.tcp://ds0pr14mb5616.namprd14.prod.outlook.com:9821/Microsoft.Exchange.MailboxReplicationService DS0PR14MB5616.namprd14.prod.outlook.com (15.20.8026.17 ServerCaps:FFFFFFFF, ProxyCaps:1FFFFFFFFFFFFFFFC7DD2DFDBF5FFFFFCB07EFFF, MailboxCaps:, legacyCaps:FFFFFFFF)' failed. Error details: 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://mail.domain.com/EWS/mrsproxy.svc' failed. Error details: The HTTP request is unauthorized with client authentication scheme 'Negotiate'. The authentication header received from the server was 'Basic realm="mail.domain.com"'. --> The remote server returned an error: (401) Unauthorized.. --> The HTTP request is unauthorized with client authentication scheme 'Negotiate'. The authentication header received from the server was 'Basic realm="mail.domain.com"'. --> The remote server returned an error: (401) Unauthorized.."

Answer 1

Hello, @Desired2Learn,

Welcome to the Microsoft Q&A platform!

The error messages you received indicates that the Mailbox Replication Service was unable to connect to the remote server using the credentials provided. This could be due to incorrect credentials or an issue with the authentication scheme used by the server.

1.Check Authentication Settings: Ensure that Basic Authentication is enabled on the Exchange server. Verify that the credentials you are using are correct and have sufficient permissions to perform the migration.

2.Troubleshoot tool: Check if the Exchange GUID property is set on the mailbox and run the Troubleshoot Microsoft 365 Mailbox Migration tool (https://learn.microsoft.com/en-us/exchange/troubleshoot/migration/moving-migration-mailbox-fails).

3.MFA and SSO: If Multi-Factor Authentication (MFA) or Single Sign-On (SSO) is enabled for the account, try disabling them temporarily to see if it resolves the issue.

4.Test Connectivity: Use the Microsoft Remote Connectivity Analyzer (https://testconnectivity.microsoft.com/tests/exo) to test the Exchange Web Services (EWS) and MRS Proxy connectivity. This tool can help identify specific issues with the connection.

5.Update Migration Endpoint: Updating the migration endpoint in the Exchange Admin Center can resolve the issue. Ensure that the endpoint settings are correct and up to date.

6.Mimecast Configuration: Since you're using Mimecast as your email gateway, ensure that it is not blocking or interfering with the migration traffic. You might need to whitelist the migration endpoints or adjust the settings in Mimecast.

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Thank you for your support and understanding.

Best Wishes,

Alex Zhang