OK, I found out the following.

After creating a new IMAP account in Thunderbird, first uncheck the "server supports subfolders and messages within folders" option in server settings. Also, it is always a good idea to restart Thunderbird after any change on an IMAP account.

Now, when I create a new folder (top level folder), I am beeing asked by Thunderbird if this folder may contain folders OR messages. This has not been the case before.

-> Select the "messages" option. Seems to work now.

Bernward

I am using the current 4.74 version of Mercury. As I understand, Mercury supports folders, that contain other folders. It does not support folders that contain both messages and other folders (Manual page 93)

However I cannot create a subfolder within an empty folder on an IMAP account. I tried Thunderbird 10 and also Outlook Express clients. I unchecked the "server supports subfolders and messages within folders" option in Thunderbirds server settings.

Within an IMAP account, I can create as much folders as I want, but no subfolders.Does anybody know how I can do so?

I also see no folders in my server's email user directories. Folders seem to be handled by some kind of database file.

Bernward