Comment 4 for bug 580300

I've found more than just a workaround ... finally !!!
The whole IMAP-implementation in Evolution has many issues, so I've given up trying to make it work.
But a new implementation called 'IMAP+' is available in the new Evolution 2.30. The 2.30 is not distributed with Ubuntu 10.04 Lucid (only 2.28), so one has to add a repository in order to get the new packages.
In a terminal write this:
sudo add-apt-repository ppa:jacob/evo230

(remember to reload your repository info ... you can write this to do it: )
sudo apt-get update

Now simply run your 'update-manager' and your Evolution packages will be upgraded :-)
(Note: If you have added the Exchange MAPI-plugin to your 2.28-installation, remove it first as it conflicts with the new 2.30)

Hope it will help you out there, who was just as desparate as I was :-)
/Corax