1. Your configuration is incorrect or database permissions incorrectly.
Since the patch for v0.1-beta2 change from 'db_mail_*' to 'db_imap_*', so edit db.inc.php
# vi config/db.inc.php
Add these lines, and modify it to accord with your IMAP server.
$rcmail_config['db_imap_dsn'] = 'mysql://dbuser:your_passwd@localhost/imap_db';
$rcmail_config['db_imap_users_table'] = 'accountuser';
$rcmail_config['db_imap_user_field'] = 'username';
$rcmail_config['db_imap_passwd_field'] = 'password';
$rcmail_config['db_imap_passwd_type'] = ''; // ''-- for Plaintext, 'ENCRYPT', 'PASSWORD'
$rcmail_config['db_imap_dsn'] is the database connect string for IMAP server, such as
"mysql://root@localhost/imap_db"
"mysql://root:pass@localhost/imap_db"
"pgsql://postgres@unix+localhost/imap_db"
"pgsql://postgres:pass@localhost/imap_db"
This tutorial is very helpful:
http://www.vulcanonet.com/soft/index.php?pack=pear_tut2. Please confirm you can connect to your database, for mysql, try
# telnet localhost 3306