I just stopped it, reinstalled everything kmail related in a synaptic 
search, and restarted it from the tde menu. It immediately reported two 
bad indices, for folders emc and spam-hold, and took 32 minutes to scan 
those 2 folders and open its gui.

I own as gene:gene with perms from 600 to 644 in the /home/gene/Mail 
subdir. It is NOT updating now for 4 days, the files 
in /home/gene/Mail/emc/cur to indicate read or important by appending 
the 
':2,S' or ':2,RS' but it is generating new indices, 2 of them everytime 
it tries to scan that folder, so it CAN create/write to that folder.

There are around 60100 messages in that folder, and the indice files are
 drwxr-xr-x   5 gene gene     4096 Mar 31 12:08 emc
-rw-------   1 gene gene 44551163 Mar 31 12:08 .emc.index
-rw-r--r--   1 gene gene   240389 Mar 31 12:08 .emc.index.ids

These 2 files have been nuked to see if a rebuild fixes it, no.
And now everthing kmail, about 8 packages, has been re-installed from the 
local archive since the mirror is missing now for several days.

Is there a fix?  Or can it be fixed short of installing a stretch 
netinstall on a new drive?

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>