$Sbases = 'OU=Users1,OU=company,DC=dommain,DC=net',
          'OU=Users2,OU=company,DC=dommain,DC=net',
          'OU=Users3,OU=company,DC=dommain,DC=net'

$daysback = (get-date).AddDays(-90)

foreach ( $sbase in $Sbases )
    {        
    get-aduser -SearchBase $Sbase -filter { (lastlogondate -like "*" -AND lastlogondate -ge $daysback -AND enabled -eq $true) } -Properties name,samaccountname,lastlogondate,distinguishedname | Select-Object name,samaccountname,distinguishedname,enabled,lastlogondate | Export-Csv activeusers.csv -Append -Delimiter ";" -Encoding UTF8 -NoTypeInformation
    }