I think on the reading side the problem is that we get:

array (
  'name' => 'Jack Strong',
  'firstname' => 'Jack',
  'surname' => 'Strong',
  'uid' => 'abcdef-0123-4567-89ab-abcdefabc123',
  'email:work' =>
  array (
    0 => 'jack@kolab.org',
  ),
  'etag' => '6d8ce421e9f0111f1437754f5aae04893acc5e59',
  'href' => '/dav/addressbooks/user/john@kolab.org/Default/abcdef-0123-4567-89ab-abcdefabc123.vcf',
  'folderId' => 'DAV:contact:f7f4db7d320d1fc06786e0b868d6b2a34',
)

but the code seems to expect something like:

'email' =>
  array (
    0 => 'jack@kolab.org',
  ),

So perhaps that's what the driver needs to return? I'm not sure where the TYPE information is supposed to go.

The writing side currently crashes for similar reasons I think (we insert an array where a string would be expected).

The Kolab3 XML objects are read like this:

$emails = $this->obj->emailAddresses();
if ($emails instanceof vectoremail) {
    $emailtypes = array_flip($this->emailtypes);
    for ($i = 0; $i < $emails->size(); $i++) {
        $email = $emails->get($i);
        $object['email'][] = ['address' => $email->address(), 'type' => $emailtypes[$email->types()]];
    }
} else {
    $object['email'] = self::vector2array($emails);
}

but Kolab4 vCards are read using rcube_vcard::get_assoc(), so the output is different. We have to support both. And looking at the code it seems that writing is also broken. I can work on this.

In D5229#66975, @machniak wrote:

The Kolab3 XML objects are read like this:

$emails = $this->obj->emailAddresses();
if ($emails instanceof vectoremail) {
    $emailtypes = array_flip($this->emailtypes);
    for ($i = 0; $i < $emails->size(); $i++) {
        $email = $emails->get($i);
        $object['email'][] = ['address' => $email->address(), 'type' => $emailtypes[$email->types()]];
    }
} else {
    $object['email'] = self::vector2array($emails);
}

but Kolab4 vCards are read using rcube_vcard::get_assoc(), so the output is different. We have to support both. And looking at the code it seems that writing is also broken. I can work on this.

Yes please. And yes, writing is also broken (crashes with the provided test).