[imp] Certificate failure

[ximm]

Hello, I'm running horde2 and imp3 in a system with debian testing.

The versions of the defferent programs are:
php4           --->   4.3.3-4
uw-imapd    --->   2002ddebian1-4
horde2        --->   2.2.3-6
imp3           --->   3.2.2-3

The thing is that uw-imapd  by default uses TLS.
I can read the mail using a client that supports TLS (i.e.:KMail), but when
I try to autenticate with horde/imp, I can't log in.

I have changed "imap/notls" by "imap" in servers.php, but still it doesn't 
work.

If I run the test.php of imp, the result is the following :
*************************************************
PHP IMAP Support Test

 server="tales.act.uji.es" user="joaquin" 
mailbox="{tales.act.uji.es:143/imap}INBOX"
array(1) {
  [0]=>
  string(170) "Certificate failure for tales.act.uji.es: self signed 
certificate: /O=University of Washington IMAP 
daemon/OU=tales/CN=tales.act.uji.es/emailAddress=root at tales.act.uji.es"
}
***************************************************
Please, how can I create a Certificate for imp?

Thank you very much.