[imp] Mail server closed the connection unexpectedly

[Stefan Suurmeijer]

Hi list,

I'm installing a new horde instance but keep running into a problem that
has me stumped.
Every time I try to login through IMP, the login fails with the message:

Mail server closed the connection unexpectedly

The problem isn't in the mailserver: it works perfectly with IMAP
clients and I've even tried connecting IMP to another IMAP server (that
works perfectly with another Horde/IMP installation), the problem
persists. So it has to be something in my horde installation.
I've tried logging in with TLS and without encryption, both give exactly
the same error message. I've tried setting the Horde log level to DEBUG,
but that didn't really give me any useful information either.
I've even copied the backends.local.php from the other Horde instance
that is working for me. Still the same error. So it has to be somewhere
in the horde installation

When I look at the Horde test page, everything is green for all
applications. So I'm out of ideas.

Anyone have any ideas what might be causing this?

Horde version is 5.2.12 with IMP H5 (6.2.16)
Relevant section of backends.local.php below

Thanks in advance,
Stefan

My backends.local.php (relevant section):

$servers['imap'] = array(
    // Disabled by default
    'disabled' => false,
    'name' => 'Cyrus IMAP Server',
    'hostspec' => 'localhost',
    'hordeauth' => true,
    'protocol' => 'imap',
    'port' => 143,
    'secure' => 'tls',
    'maildomain' => 'mydomain.com',
    'smtp' => array(
        'auth' => true,
        'horde_auth' => true,
        'host' => 'localhost',
        'lmtp' => false,
        'port' => 25,
    ),
    'spam' => array(
    ),
    'admin' => array(
         'user' => 'cyrus',
         'password' => 'cyruspassword',
         'userhierarchy' => 'user.'
    ),
    'acl' => true,
    'cache' => false,
    'quota' => array(
        'driver' => 'imap',
        'params' => array(
            'hide_when_unlimited' => true,
            'unit' => 'MB'
        )
    ),
    'special_mboxes' => array(
         IMP_Mailbox::MBOX_DRAFTS => 'Drafts',
         IMP_Mailbox::MBOX_SENT => 'Sent',
         IMP_Mailbox::MBOX_SPAM => 'SPAM',
         IMP_Mailbox::MBOX_TEMPLATES => 'Templates',
         IMP_Mailbox::MBOX_TRASH => 'Trash',
    ),
    'autocreate_special' => false,
);


Log information:

cat /tmp/imp_imap.log
------------------------------
>> Sat, 12 Nov 2016 21:57:44 +0000
>> Connection to: imap://localhost/
>> Server connection took 0.0003 seconds.
>> ERROR: Server closed the connection.
------------------------------
>> Sat, 12 Nov 2016 21:57:47 +0000
>> Connection to: imap://localhost/
>> Server connection took 0.0003 seconds.
>> ERROR: Server closed the connection.