kmail really slow while typing

[Luca Ferrari]

Hi,
using KDE 4.5 on Kubuntu 10.04, but this appears quite often when a new KDE 
release is installed: KMail becomes really slow when typing, I mean the text 
appearing on the screen is often 2-3 seconds late of when I typed it. Someone 
told me it was a network problem, but I'd like to know if there's a 
configuration option or something to make this annoying behaviour to stop.

Thanks,
Luca