rsync, ssh and DSA key

[khabot]

hi all
I have generated the key in the source server(10.78.0.107)
ssh-keygen -t dsa -C "root at 10.78.0.107"
I have added this key to authorized_keys2 of the destination
server(10.78.0.117)
cat id_dsa.pub >> /root/.ssh/authorized_keys2
but when I execute 
rsync -avz -e ssh root at 10.78.0.107:/var/mail/ /var/mail
in the destination server I asck me for the password
How to avoid this in order to automate this script.
Thanks.