Configuring apache for squirrelmail following this tutorial is not enough. You’ll need to configure squirrelmail too. Edit your /etc/squirrelmail/config_local.php file and paste the following configuration:
// courier-imap settings $imap_server_type = 'courier'; $default_folder_prefix = 'INBOX.'; $trash_folder = 'Trash'; $sent_folder = 'Sent'; $draft_folder = 'Drafts'; $show_prefix_option = false; $default_sub_of_inbox = false; $show_contain_subfolders_option = false; $optional_delimiter = '.'; $delete_folder = true; $force_username_lowercase = false; // other settings $default_charset = 'iso-8859-1'; $lossy_encoding = false; $sendmail_args = '-i -t'; $encode_header_key = ''; $hide_auth_header = false; $plugins[3] = 'filters'; $abook_global_file = ''; $abook_global_file_writeable = false; $addrbook_global_dsn = ''; $addrbook_global_table = 'global_abook'; $addrbook_global_writeable = false; $addrbook_global_listing = false;