capacity/performance question about Kmail

[Claude Jones]

I run several Linux boxes now, including two FC4 machines. I do all my mail 
reading on them, now, though I leave messages on the servers and only 
download to my Windows box for archival. (I have mail archived as far back as 
early 90's) I've noticed a huge discrepancy in performance between Outlook 
vs. Kmail and I wonder what others are experiencing. 

Currently, I have over 20,000 messages on one FC4 box and nearly that many on 
the other. Leaving aside the question of why, here's my observation/question:
With Kmail, my fedora-list folder, for example, currently contains over 13,000 
messages. I leave my search bar open all the time. If I want to retrieve an 
old post that I remember as having pertained to a current problem, I can 
start typing in to the search bar and immediately, Kmail begins narrowing the 
search options and producing a list of relevant messages - I mean immediately 
- there is no lag, the response seems instantaneous. 

To search a folder in my Outlook archive, even a much smaller folder, takes 
many moments, sometimes over a minute, if the folder is 'large' - by large, I 
mean over a 1000 messages. For this reason, I have archiving turned on, and 
messages over 3 months old are sent to archive, but of course that then means 
multiple searches if I'm looking for an older message. 

So, my question: how large can Kmail folders get before they start to slow 
down searching? I find this performance remarkable, and I'm just wondering 
what the limits are? 
-- 
Claude Jones
Bluemont, VA, USA