I recently switched from Thunderbird to EM and am generally quite content.
But I tend to open mails that I will work on later in a new window (doubleclick) and keep them in the queue. I mark them with flags/tags too, but I like to keep them “on the screen”.
My problem is that after a reboot, EM does not reopen or keep track of the opened mails, as for example Thunderbird did with the Tabs (or pretty much any Browser too).
I could not find this as a regular option somewhere, and would really appreciate a feature like that.