To reproduce:

Symptom 1 -
Go into eMail and click the New Folder tab.
Enter a folder name.
Click the Cancel button.

Result - the folder gets created.
Expected result - the action should be cancelled.

Symptom 2 -
Go into eMail and click the New Folder tab.
Don't enter anything.
Click the Cancel button.

Result - the folder name field is outlined in red, and there is a message that a folder name is required.
Expected result - the action should be cancelled.

A patch is attached.