Specify relay for single domain

[Blake]

I have a relay server which is doing great relaying email except a 
specific domain.  Instead of pointing to the new google aspmx servers it 
is going to an old postini.  I have made a request that the MX record be 
updated but due to vacations of the individual in control it could be 
mid to late next week before this change is made.  For the short term I 
would like to explicitly forward that one domain instead of setting the 
relay server to send all mail one direction.

Thanks,
Blake