ADD extensionAttribute

If you have different upn names , than your domain server name and you need to use different upn-s for ldap queris you can add sammaacountname + server domain name to custem attributes.

In file atribute.txt write users sammaccountnames.

Import-Module ActiveDirectory
$Users = Get-Content c:\tmp\atribute.txt
ForEach ($User in $Users) {
$username = Get-ADUser -Server test.local -Identity "$user" -Properties  samaccountname |select -ExpandProperty samaccountname
Set-ADUser -Server test.local -Identity "$user" -Add @{extensionAttribute13="$Username@test.local"}
}