ExRecipNotFound; not found after disabling / recreating mailbox in exchange - x500 not working

It's better to deal with just updating the GAL/OAB and making sure everyone also updates their OAB as well. Once you update the one on the Exchange server, you can test with OWA first to make sure client OAB updates will fix the issue

You can follow this article from Microsoft to do so:

How to Quickly Rebuild an Exchange 2010 Offline Address Book

Follow it down to the Outlook portion, but before you bother with updating an Outlook client, try Outlook Web Access first, and test and verify you can send to the new mailbox. Then mess with updating the Outlook clients (or just wait 24+ hours, and they will get it automatically).

P.S. Personally, when I've run into this in the past, I don't mess with the X.500 address at all. It is a little of a PITA at first, because after you do this new emails will work, but existing emails that original mailbox sent IF replied to will fail. This will be a helpdesk issue for a few days explaining that people will just need to create a new email to the "new" mailbox instead of replying to the old. After about a week, it pretty much becomes a non-existent issue.