All windows of Kmail in the task manager on the panel have the cogwheel icon, which is typically displayed when there is no icon defined for a file or application. Reproducible: Always Steps to Reproduce: 1. Open Kmail window and look at the task bar. 2. Create a new mail or reply to an email. Actual Results: The Kmail application and the mail composer have the cogwheel icon. Expected Results: The application icon should be used. Kubuntu 15.10, x86_64.
Kmail version is 5.0.2.
Created attachment 95256 [details] Kmail windows in the task bar having incorrect icons
it works here in master. So I don't know what is broken in your ubuntu. But perhaps a bug in plasmashell (fixed for sure from longtime)
That is the case on at least two of my machines, both were recently upgraded from Kubuntu 15.04 to 15.10.
Also, for other applications icons look fine. I can see the described problem only with Kmail.
The problem is fixed in Kubuntu 16.04.