Empty group listing for Zimbra server

[Alberto Luaces]

Hi,

I have successfully configured gnus to read email from gmail with nnimap. Now 
I also have another IMAP account in a Zimbra server, but the group list is 
always empty. Following nnimap logs, I saw that it uses the LSUB command in 
order to display the available folders. While in gmail all folders are listed 
this way, in the Zimbra server an empty list is returned. It only shows the 
lists of folders with the LIST command.

What do I have to do to get my folders in gnus with nnimap?

Thank you,

Alberto