I have One user that internal email is good.
Any message sent from the outside gets a bounceback message:
Unknown address error 550-'No such recipient' (delivery attemps:0)

Gwia log shows:
06:08:31 EF2D DMN: MSG 24121586 Recipient unknown: problemuser@mydomain.com

Why only One?
GWCheck runs clean.
No Pending Operations from Consoleone.