Demo site not working with my IMAP server

[avitabile@chemistry.unina.it]

I have an IMAP server chemistry.unina.it running PMDF by Process
Software.
   I try to access it from horde demo site, and I systematically
get a login failure, with a suggestion either the username or password
are wrong. Of course, they work with any other IMAP client.
   The same box is also running IMP 2.2.6 and I can access the IMAP
server using it.
   What is the problem with access from the demo site?
                                Gustavo Avitabile