Version:           unspecified (using KDE 4.3.2) 
OS:                Linux

Moving several messages from one imap folder to another is already very slow in kmail, but the worst thing is, it gets proportionally slower the more messages are selected. It seems as if at first all individual move operations are queued in a list at once (that takes some time), and then this list is processed one message at a time, and somehow it takes longer to select the next operation out of this list, the longer this list is. Moving a few thousand messages on a local imap server (1Gb connection) can take hours!!

Reproducible: Didn't try

Steps to Reproduce:
Chose a IMAP folder with many messages (for example from a mailing list).
Create a second folder.
Select 100 messages from the first folder and move them to the second folder. Time the operation.
Select 1000 messages from the first folder and move them to the second folder. Time the operation.

Actual Results:  
The second operation (1000 messages) takes much more than 10 times the time of the first operation (100 messages).

Expected Results:  
The second operation (1000 messages) should take approximately 10 times the time to complete than the first move operation (100 messages).

1.- When clicking on the arrow button on the status bar to show the list of pending operations while moving a few thousand messages, kmail freezes a very long time to show the list (which is very long). It seems to me that this code is not scaleable and the whole job processing should be re-designed.

2.- IMAP supports copying multiple messages in one command. It seems utterly inefficient that kmail apparently does not use this feature.

3.- I remember doing the same sort of operations in kde-3.5 in the past and it didn't even be nearly as slow, although my computer was much slower back then.