[imp] Cannot access IMAP Server

[Wim]

Hi,

I am trying to connect Horde/IMP to my IMAP server but I always get 'Login Failed'. I am sure that my
credentials are correct as these are working fine when I connect to my IMAP Server with a Mail Client
(Mozilla).
Horde is running on the same server as my IMAP Server.
This is my config in servers.php

$servers['imap'] = array(
    'name' => 'IMAP Server',
    'server' => 'localhost',
    'hordeauth' => false,
    'protocol' => 'imap/notls',
    'port' => 143,
    'folders' => 'INBOX.',
    'maildomain' => 'example.com',
    'smtphost' => 'localhost',
    'smtpport' => 25,
    'dotfiles' => false,
    'hierarchies' => array()
);

This is what I get in the horde.log

HORDE [error] [imp] FAILED LOGIN x.x.x.x to localhost:143[imap/notls] as 'user' [on line 247 of
"/root/horde/imp/lib/Auth/imp.php"]
HORDE [info] [imp] x.x.x.x failed [on line 31 of "/root/horde/imp/login.php"]

Hope anyone can help

Thanks
Wim