Since it finds no email address or anything else, I would say the alias is not located within the same scope of the root directory.
And since it finds no email address, the email would likely be getting sent to the machines email address, not into nothingness (I assume they use Send to self.)
I would look server side at the alias settings, use something like Softerrra LDAP browser so you can view the lookups and see all the details for both.