Issues occur with connection timeouts when migrating from Exchange servers to Office 365 through the LoadMaster in Exchange 2010 -2016.
Bypass the LoadMaster
Customers can arrange maintenance window to complete chunks of their mailbox migration.
The NAT entry for the public Office 365 IP will need to be changed from the VIP address directly to the real server for the extent of the mail box migration.
Increase the MRS timeout value
Increasing the MRS proxy timeout value has worked in Exchange 2010 deployments.
Issue Power Shell Commands on Exchange server
In exchange 2016, it is necessary to issue the following Power Shell commands to migrate each mail box:
Step 1 - Authenticate with Office 365: $cred = Get-Credential – in the format of firstname.lastname@example.org
Step 2 - Create Session with Office 365: $Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $cred -Authentication Basic -AllowRedirection
Step 3 - Authenticate with local Exchange server: $cred=get-credential – Credentials should be in format Domain\username
Step 4 - Specify Mailbox to migrate to Office 365: New-MoveRequest -identity Username -Remote -RemoteHostName webmail.domain.com -TargetDeliveryDomain domain.com -RemoteCredential $cred -BadItemLimit 0 -LargeItemLimit 0