When trying to do a redirect on a mailbox externally, it was not processing the email.
Internal was fine.

Apparently forwarding / redirects to external domain names is disabled by default in Exchange 2007 and 2010.

To change this setting, open the Exchange Management Console, and drill down to the Organization Configuration -> Hub Transport.  Under the Remote Domains tab, open the Default domain.

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Then, on the format tab, check the “Allow automatic forward” box.

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Alternatively, from the Exchange Management Shell (PowerShell rocks!), this will do the trick:

set-remotedomain -identity Default -AutoForwardEnabled $true