Export is essentially a snapshot of your archive. If the contents are constantly being added to after the export BEGINS, there would need to be another differential export after the FIRST export completes in order to GET all the new email that was archived since the export began. This would BECOME a loop as new data is continually added, so the best SOLUTION is to "freeze" the contents of the archive during export. This also means that selective purge and retention purge will be suspended.

Export is essentially a snapshot of your archive. If the contents are constantly being added to after the export begins, there would need to be another differential export after the first export completes in order to get all the new email that was archived since the export began. This would become a loop as new data is continually added, so the best solution is to "freeze" the contents of the archive during export. This also means that selective purge and retention purge will be suspended.