I switched my mom over to Ubuntu a couple months ago and I have already had to rescue her email 2 times. The problem is when a folder in Evolution surpasses 2 GB, Evolution can't access it anymore. Evolution allows this without any warning and then that folder stops working without any information. The end user ends up lost and doesn't know how to recover the 2+ GB of email that is now inaccessible. There is a program called archivemail in the universe repository that will let a user archive mail stored in MBOX format. I've had to use this to recover my mom's email.
Evolution should warn the user to archive their mail before it goes past the 2 GB limit. An even more user friendly approach would be to automatically archive email folders for the user. Of course, Evolution could also be fixed to allow more than 2 GB in a folder.
Please fix this as it drives my mother and ultimately me nuts every time it happens. I can't imagine how many other people have run into this and don't know how to recover from it.