At some point we seem to have lost the ability to shut down mailboxes. I've disabled the AD account, andtriple-checked that nobody, including SELF, has Associated external account checked. Yet the mailbox continues to receive mail both internally and externally. I could obviously delete the mailbox, but we'd prefer to keep it around a little longer. Everything I've read suggests that disabling the box with no associated external account should do the trick, but it's not.This had been working before and I'm not sure what occured that it's no longer working.

What version / SP of Exchange?

I'm positive we're running Exchange 2003, but am a little uncertain about the Service Pack. If I select 'About' in the management console it says Version: 6.5.7638.1

Why don't you set the delivery restrictions on the mail box not to accept any e-mail. That is a easy way to stop mailflow to that mailbox.