The Remote Server Returned an Error (401) Unauthorized
Authentication and credential issues preventing migration access.
Error Message
Migration Authentication Error
The request failed. The remote server returned an error: (401) Unauthorized
This error occurs when the migration service cannot authenticate with the source or target environment.
Authentication Flow
Mail Migration Causes
Exchange / Office 365 Issues
Azure AD application lacks "full_access_as_app" permission for Exchange.
Username or password in the connector is wrong or has changed.
Multi-Factor Authentication on the migration account blocks automated access.
SSO systems redirect authentication, preventing direct login.
Migration account lacks valid Office 365 or Exchange license.
Exchange on-premises has legacy authentication turned off.
File Migration Causes
OneDrive / File Storage Issues
The credentials stored in the connector are incorrect or expired.
Migration account doesn't have access to the user's OneDrive.
The Cloudiway application isn't properly installed on the tenant.
Solutions
For Mail Migration
Verify Credentials
Log into your Exchange server or Office 365 via browser using the same credentials configured in the connector.
Disable MFA
Turn off Multi-Factor Authentication for the migration service account. Use a dedicated service account with MFA excluded.
Bypass SSO
Exclude the migration account from SSO policies or configure direct authentication.
Assign Licenses
Ensure the migration account has a valid Exchange or Office 365 license.
Enable Legacy Auth
For Exchange on-premises, enable legacy authentication protocols to allow EWS connections.
For File Migration
- 1. Test login at
portal.office.comwith connector credentials - 2. Grant migration account access by running preprocessing
- 3. If needed, recreate the connector to reinstall the application
- 4. Alternatively, manually add the certificate to the Azure app
For SharePoint Migration
- 1. Add your administrator to Site Collection Administrators
- 2. Create the target site collection before starting migration
- 3. Verify the admin has Full Control permissions