[horde] Automatically add sent mail ID in address book

[Suhag Desai]

Hi all,
I have a little problem regarding address book.
I want to add automatically sent mail email-id in dafault address book.
Let me explain
suppose i sent one mail to abc at test.com ,, so abc at test.com ID should be add automatically in dafault address book.
How to do this ?
I have tried with /horde/imp/config/pref.php with below option

$_prefs['save_recipients'] = array(
    'value' => 1,
    'locked' => false,
    'shared' => false,
    'type' => 'checkbox',
    'desc' => _("Save recipients automatically to the default address book?"));

BUT did not work
Kindly let me know the solutions

thanks 

suhag