IMAP, gnus, and the messages that don't want to go away

[Pierfrancesco Caci]

Hello,
I use gnus to read my mail with the IMAP backend. I have some messages
that keep reappearing in the summary even if the message itself was
deleted long ago. Gnus will let me mark them as expirable, but it will
not let me delete them completely. As I said, the body of the mail is
not there, just gnus think it is. How can I have gnus realize that
those imap groups are empty ?

Thanks 
Pf 

-- 
Pierfrancesco Caci