IMAP Folder Manager was created to manage IMAP folders for large user bases. It can list, create, delete, and rename folders, count messages in a folder, move or copy all the messages from one folder to another, and empty a folder. It supports PROXYAUTH for easy user management and has a simple but powerful argument interface, able to do things like "create folder2, move messages from folder1 to folder2, and delete folder1" in a single compact line.
