ENVIRONMENT:
I am using evolution 2.30.2 with Debian amd64:

ii  evolution                                     2.30.2-1                             groupware suite with mail client and organizer
ii  evolution-common                              2.30.2-1                             architecture independent files for Evolution
ii  evolution-data-server                         2.30.2.1-1                           evolution database backend server
ii  evolution-data-server-common                  2.30.2.1-1                           architecture independent files for Evolution Data Serve
ii  evolution-dbg                                 2.30.2-1                             debugging symbols for Evolution
ii  evolution-exchange                            2.30.2-1                             Exchange plugin for the Evolution groupware suite
ii  evolution-plugins                             2.30.2-1                             standard plugins for Evolution
ii  evolution-webcal                              2.28.1-1                             webcal: URL handler for GNOME and Evolution

PRECONDITIONS:
You have an IMAP folder configured and you can fold and unfold the folders.

STEPS:
1- Get a new email
2- Wait for the notification bubble to dissapear
3- Click on the blinking notification icon
4- Try to fold and unfold folders.

EXPECTED:
You can fold and unfold.

ACTUAL:
You cannot fold and unfold your folders.

FREQUENCE:
Always.