[imp] Dynamically selecting an IMAP server for authentication in IMP5

[Arminas]

Hi,

We're using imap servers for an authentication. I'm trying to implement
automatic imap server selection/detection for authentication, but I wasn't
able to find any tutorial about it for IMP5. An article in
http://wiki.horde.org/ImapSelect seems like is "out of date". So I have
some questions:

Which application should alter authentication server's string to the right
one - weather the preauthenticate function must be defined in
horde/config/hooks.php, or in horde/imp/config/hooks.php? If IMP app should
handle this, then what must be done to call this hook function? If I define
simple function
      public function preauthenticate($userId, $credentials) { return
false; }
in imp/config/hooks.php, I can see it is never called.

Which variables must be set so IMP can know where to try to authenticate?
Probably this piece of code won't do the work:
 // Set IMAP server values.
         foreach (array('server', 'folders', 'namespace') as $key) {
             $_SESSION['imp'][$key] = $servers[$server[0]][$key];
         }



Horde (horde) 4.0.13
Mail (imp) 5.0.17


Thanks in advance!
Arminas