Qmail delivery with maildrop

[eschoeller]

I have a crazy one...
I have a username (blah) that I want to disable, however I have several aliases (blah-something, blah-something2 etc) that I want to remain active.
I would like to be able to login using the username blah, and be able to see imap folders for the aliases, but when mail gets sent directly to blah@host.com I want the mailserver to respond with 'Unknown User' or 'Invalid Mailbox' not, 'Unable to open mailbox'
I do global filtering with maildrop, but it doesnt seem like editing my configuration will allow me to do this...

Any help / suggestions would be greatly appreciated.
running qmail+maildrop+SA+courier-imap