Hi @Mohamed Benhaddou ,
Welcome to our Q&A forum!
By research, this error appears when Office 365 is not able to communicate with on-premises server where MRS (Mailbox Replication service) service is on.
Below I have mentioned some checklists to investigate:
- First thing be sure you are using correct on-premises account credentials for the endpoint.
- Run Remote Connectivity Analyzer for Autodiscover service in Exchange Server.
- Check that the service is running and WSecurity is allowed. For this step you can use
Get-WebServicesVirutalDirectory | FL MRSproxyEnabled,WSsecurityAuthentication command.
If is show$False
runSet-WebservicesVirtualDirectory -Identity "Server Name\EWS(Default Web Site)" -MRSproxyEnabled:$True -WSSecurityAuthentication:$True
When these steps are completed, you can restart the migration process again.
Hope the above can help you and feel free to let us know if you have other questions.
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