Version:            (using KDE Devel)
Installed from:    Compiled sources
OS:                Linux

I wrote an email for about one hour and then quit kontact which crashed.

I did not save the message manually because relying on the fact that kmail is supposed to do this every few minutes. Actually the latter was a point against introducing the possibility to save a message without closing it.

Unfortunately I cannot say whether kmail did not save the opened message on exit, or whether it saved it in a way that would lead to its deletion on the event of kontact crashing when exiting.