I am having a similar issue with one mail box (firstname.lastname@example.org) not recieving email from one of my other users (email@example.com). See bounce back below. The jennifers address was deactiviated for a time then reactivated. All other users are normal and jennifers recieved mail from all other addresses. Checked blocking and forwarding in jennifers account, all normal. Any Ideas?
Diagnostic information for administrators:
Generating server: W14HUB-CH2-A2.w14a.comcast.net
IMCEAEX-_O=W14A_OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FYDIBOHF23SPDLT+29_CN=RECIPIENTS_CNfirstname.lastname@example.org #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##