Set-UPNBasedOnSamAccountName.ps1

#Change UPN to SamAccountName@specifieddomain
# useful if needing to switch UPNs or to set UPNs before using DirSync for OnPrem to O365 Directory Synchronization
# Should add domain, i.e. contoso.com to UPN Suffixes in properties in Active Directory Domains and Trusts first

Import-Module ActiveDirectory;get-aduser -filter {Name -like "*"}|foreach{Set-ADUser $_ -UserPrincipalName ("{0}@{1}" -f $_.SamAccountName,"contoso.com")}