Since IMAP folders exist on the server, and opening them or checking them takes time, you need fine-grained control over the way that you use IMAP folders. That's why Evolution has an IMAP subscriptions manager.
To use it:
Select Tools->Subscribe to Folders.
If you have accounts on multiple IMAP servers, select the server where you'd like to manage your subscriptions. Evolution will display a list of available files and folders.
Select a file or folder by clicking on it. You will want to select at least the INBOX folder. Depending upon the way your IMAP server is configured, the list of available files may include non-mail folders. If it does, you can ignore them.
Click the Subscribe to add it to the subscribed list.
When you have subscribed to the folders you want, close the window.