Version:            (using KDE KDE 3.3.91)
OS:                Linux

When I ricght click on the column-titles in the sent-folder, I get presented a list:

attachment
.
.
sender

When I click on sender and open the dialogue again I get:

attachment
.
.
x recipient

Both. sender and recipient columsn are shown, yet there is only an activated recipient entry. Recipient is enabled anyway.
To disable the sender columen was has to disable the recipient entry, which then changes to sender again.

What I would expect is two entries:
recipient
sender

If both are enabled:
x recipient
x sender

and not just.
x recipient