I've just completed a migration to SBS 2011 from SBS 2003. All the users emails are working fine except one. They can send email externally fine and can send mail internally through OWA, but not through the Outlook client.
I deleted the OST and let the system recreate it, but it still has the same issue.
Here are the results from the DNR
Generating server: MPPDC-EXCHANGE.mppdc.local
IMCEAEX-_O=MPPDC_OU=FIRST+20ADMINISTRATIVE+20GROUP_CN=RECIPIENTS_CN=LLODING@mppdc.local
#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##
None of the other local user accounts have a problem sending mail the that email address. And it works fine from OWA.
What do I try next?