When i tried to move user's mailbox from on premise to Office 365 and getting error " The operation couldnt be performed because object user1@Domain.com couldnt be found on copr.man.prod.outlook.com".
I checked on user's account on Office 365 admin portal, user's account was reflating and seems fine.
This error indicate user's Active Directory account did not sync on Azue Active Directory properly.
For resolving this issue i have to remove user from online (Azure Active Directory) completely than next DirSync will take care to syncing the user's account into Azure Active Directory.
For removing user's account from Azure Active Directory i have run following command :
1. First connect the Office 365
$UserCredential = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
2. Run below command
Remove-Msoluser -UserPrincipalName email@example.com
3. Than run command :
Remove-Msoluser -userPrincipalName firstname.lastname@example.org -RemovefromRecycleBin
Once run all command, now wait for next DirSync replication or you can force the DirSync.
Once DirSync completed try to move the mailbox from on premise to Office 365.