If the domain was created using the Directadmin UI, then the directory should have been created. But you still didn't state if the directory actually exists. There are other reasons the stat might have failed besides the directory missing, like invalid permissions leading up to that directory. Of course if that was the case, I would have expected other errors being reported when someone sends/receives emails, since they require the ability to read the /etc/virtual/$domainname/passwd file.
