$user1 = "user.1"
$user2 = "user.2"
$user3 = "user.3"
$user4 = "user.4"
$folders = (Get-PublicFolder -recurse | ? {$_.identity -like "*customer*"})

foreach ($folder in $folders){
    add-publicfolderclientpermission -identity $folder -accessrights Owner -user $user1; Write-Host "setting $user1 for $folder"
    add-publicfolderclientpermission -identity $folder -accessrights Owner -user $user2; Write-Host "setting $user2 for $folder"
    add-publicfolderclientpermission -identity $folder -accessrights Owner -user $user3; Write-Host "setting $user3 for $folder"
    add-publicfolderclientpermission -identity $folder -accessrights Owner -user $user4; Write-Host "setting $user4 for $folder"
}