SELECT MONTH(LogDate) AS [Month]
, DATEPART(HOUR, LogDate) AS 'Hour'
--, Sender
--, mbx.MailboxDisplayName As 'Display Name'
--, mbx.OrganizationalUnit as 'Organizational Unit'
--, mbx.Department as 'Department'
, COUNT(MessageId) As 'Messages Sent'
FROM Traffic t
INNER JOIN MessageList m ON t.TrafficId = m.TrafficId
INNER JOIN RecipientList r ON r.RecipientListId = m.RecipientListId
INNER JOIN Mailbox mbx on mbx.EMailAddress = t.Sender
WHERE t.[Sent] = 1
AND (LogDate >= '3/26/2016 4:00' AND LogDate < '3/28/2016 4:00')
AND EXISTS
(
SELECT 1 FROM Mailbox m2 WHERE m2.EMailAddress = t.Sender
AND OrganizationalUnit IN ('your.domain.com/US GROUP/Users/Accounts', 'your.domain.com/US GROUP/Users/Accounts_2')
)
--GROUP BY CAST(LogDate AS DATE), t.Sender, mbx.MailboxDisplayName, mbx.OrganizationalUnit, mbx.Department
GROUP BY MONTH(LogDate), DATEPART(HOUR, LogDate)
ORDER BY MONTH(LogDate), DATEPART(HOUR, LogDate)