Click "Display Options" and ensure that "Show grouping by columns option" is
checked, then you can see the grouping bar just above the MailWasher column
title bars.
Drag the column headers into the bar to get MailWasher to group the
emails, or drag away to remove them.
Alternatively, right click on the column header to 'Group by..' or remove the column header group.
NB
Comments
Problem Solver
Any column that relates to a ‘date reference’ is subject to this behavior.
Fix the view by [right-click] on any date related column header [e.g., Received / Sent];
When there’s a check mark in the “sort by” box is check, un-check it
Rickey Cummins
How do I get rid of the groupings in the inbox that group by "today", "last week", "last month", etc. This is really irritating for me.