For info, I checked if the messages were really physically duplicated in the folders, or only in akonadi cache ; they are duplicated each 17 times physically.
Using maildir, each mail has a distinct name like '1350381035.R668.linux', '1350352842.R783.linux:2,S' or '1349859050.R458.linux:2,FS'.
This problem still means NOGO for use in a production environment.
For info, I checked if the messages were really physically duplicated in the folders, or only in akonadi cache ; they are duplicated each 17 times physically. R668.linux' , '1350352842. R783.linux: 2,S' or '1349859050. R458.linux: 2,FS'.
Using maildir, each mail has a distinct name like '1350381035.
This problem still means NOGO for use in a production environment.