Updating ProxyAddresses, Example 1

Import-Module ActiveDirectory
 
$newproxy = "@domainname.com"
$userou = 'ou=Users,ou=Directory Sync,ou=Org,dc=domain,dc=domain,dc=com'
$users = Get-ADUser -Filter 'Name -like "Test"' -SearchBase $userou -Properties SamAccountName, ProxyAddresses 
 
 
Foreach ($user in $users) {
    Set-ADUser -Identity $user.samaccountname -Add @{Proxyaddresses="SMTP:"+$user.samaccountname+"."+$newproxy}
    }