To add a little...
You can also auto create LearnAsSpam folder if you need it.
Just enter:
// display these folders separately in the mailbox list.
// these folders will automatically be created if they do not exist
$rcmail_config['default_imap_folders'] = array('INBOX', 'Drafts', 'sent-mail', 'junkmail', 'Trash', 'LearnAsSpam');
P.S.: I use RC and HORDE but i don't have a sent-mail folder. I have a Sent folder. But it could be the fact that i installed RC and then horde.