Have been using KMail on Kubuntu 14.04 for a few years. Upgraded to Kubuntu 16.04.1

KMail Version 5.1.3 using KDE Frameworks 5.18

Started to use KMail. There is no subject appearing on any message list views. If I right click, the word 'Subject' is greyed out. Just have Sender and Date. The aggregation is Standard Mailing List, theme is classic. Please advise how to include the Subject in all message lists.

The message list is shown as flat display. There is no threading, and when I go to change the Aggregation, the groups/threading is greyed out, disabled. Can't be changed. Please advise how to change the message list view, so that it is shown as threaded by subject, so that I can see all the emails for that subject.

Problem solved. I did try adjusting the columns a few times, but no luck. The "Subject" column was totally hidden. Able to see it now by moving the Sender column to the right.