It would be extremely useful if the column sorts in Mailwasher were order preserving. I.e. when the user clicks on a column to order on it, any group that has the same value in the sorted column should retain exactly the same ordering as they had before the sort. E.g. if I order on the "sent" column then on the "account" column, everything within each account should be in date order.

All multi-field sorts in all products in all operating systems on all computers should operate this way. Almost none do. At one time they all did. Then came the PC.