When creating a production or export set, you set the "Volume Partition Sorting" option to sort by SentDate, but when you review the export, there are items out of order.
You will need to apply two sorting options to achieve the desired output.
First apply it to sort by "Attachment" and then sort by "SentDate".
Typically when items are out of order, it is because an older email is attached to a newer email. That attached email has its own SentDate and therefore is chosen to be exported sooner than the email it is attached to. Summation Pro will always keep families together during an export, so the parent email is exported in line with the attached email, causing the export to seemingly not be sorted by SentDate correctly.
By applying the Attachment sorting option, you will be telling the system to evaluate the Attachment Field first. This is a True/False field, therefore it will process all items with an Attachment value of False, which are the parent documents. It will then look at the SentDate of all the parent emails and run the production in order based on those dates. The attachments will be pulled in line with their parent emails automatically.