SELECT DisplayName,EmailAddress,LastMessageSent
FROM OpenExchangePSQuery(
    POWERSHELL, '
$Mailboxes=Get-Mailbox -ResultSize Unlimited | Where {$_.RecipientTypeDetails -eq "UserMailbox"}

foreach ($m in $mailboxes)
{

$name=$m.name

$emailaddress=$m.primarysmtpaddress

$messagesSent=Get-MessageTrackingLog -EventId "Send" -ResultSize Unlimited -Start (Get-Date).AddDays(-3) | Where {$_.Sender -icontains "$emailaddress"} | Sort timestamp -desc | select -First 1

foreach ($message in $messagesSent)

{$Result = New-Object PSObject -Property @{
DisplayName = $name
EmailAddress = $emailaddress
LastMessageSent = $message.timestamp

}

$Result | Select DisplayName,EmailAddress,LastMessageSent

}

}
              ', POWERSHELL
)