The issue is that you are referring to the column SentDateTime individually and in aggregated columns in the group by and count functions.
You may be able to simply turn off sql_mode=only_full_group_by in your server since you are on a dedicated host to resolve this issue. Otherwise you might have to restructure your SQL statement and possibly break it into separate SELECT statements to get the data you want efficiently.
I couldn't get in with the FTP information provided, so I couldn't look at the page directly.
Did this help? Tips are appreciated...
