Bulk email domain change

I am trying to find the PS script to update multiple users to a new domain in office 365, leaving existing domains as the alias. I have used a command in the past successfully:

Import-CSV "C:\temp\Users.csv" | ForEach {Set-Mailbox $_.UserID -EmailAddresses $_.NewEmailAddress,$_.UserID,$_.Proxy1,$_.Proxy2}

Now it will not work. can anyone tell me what is now wrong with it?