On Fri, Nov 2, 2012 at 10:17 AM, Tim wrote:

I've not used kmail for years, but it occurs to me that if you have
options to immediately delete mail, that it would be logical for the
trash folder to be removed if you have such a setting set.  So, you
could look for such settings.

If there is such a setting, I can't find it. In Settings->Configure KMail->Misc->Folders there are a couple of checkboxes -- ''Ask for confirmation before moving all messages to trash" and "Empty local trash folder on program exit" -- but nothing that tells me where to find the trash folder's contents in any event.
 
It also occurs to me that you could have accidentally deleted a trash
folder, or accidentally dragged and dropped it into another folder.

It could be worth your while to create another user account on your
system, log in as that user, then fiddle around with kmail, without
risking changing what's currently still working, and without risking
losing your mail.  You could try to deliberately break things, to see if
you can discover how your trash folder disappeared, where it might have
gone, and how to get it back.

Ok. I just did a totally fresh install in a VM. KMail definitely only has "inbox," "outbox," and "sent-mail" under Local Folders. So it's not like I accidentally deleted it.

I tried creating a folder called "Trash" and deleted a message. Still not there. I tried "Search in all folders" for something that positively must match a deleted message. Nothing.

I'm beginning to think that the KMail developers are all snickering to each other as they watch me through my webcam.

-Alan