My evolution client has recently started regular folder synchronisations.
This is on a machine I use all day at work, so
a) my mail folders are reasonably large (1000's of messages), and
b) having my CPU busy for up to a minutes whilst evolution does it's thing is largely unacceptable.

Admittedly this is version 2.0.4, as I'm still running Debian Sarge. But it never used to do this. I haven't changed any settings, nor can I find any setting which seems to be relevant.

I wonder if there's an "Evolution" way of solving this before I start exploring whether I can somehow `nice` evolution...

The only time I've seen something like that is when I've had trouble getting (back) to a server when a download of mail has been interupted. But it's usually only once or twice until it cleans itself up.