[BlueOnyx:11676] Vacation messages

[Gregg]

I have a user that is trying to use a vacation message.
The setup looks all good, but when the system tries to send back a message,
it gets stuck in clientmqueue with the following error:
The original message was received at Fri, 16 Nov 2012 11:05:47 -0700
from username at localhost

   ----- The following addresses had permanent fatal errors -----
senderusername at senderdomain
    (reason: 553 5.3.0 <username at localdomain>... No such user here)
    (expanded from: senderusername at senderdomain)

All aliases seem to be working good.
It seems like the vacation message script is not picking up the user domain,
and it's trying to use the main domain for the server and it's not finding
the user.
How can this be fixed?
Thanks.