[exim] Access denied for user: 'root@localhost

Hi,

When I tried to send email thru exim, I got an error about Access denied
fro user: 'root@???' error.
The complete logging msg is shown as below:

cram authenticator failed for ([192.168.4.235]) [192.168.4.235]: 435
Unable to authenticate at present (set_id=postmaster): lookup of "select
clear from passwd where email = 'postmaster' and clear != '' and smtp =
'yes'" gave DEFER: MYSQL connection failed: Access denied for user:
'root@???' (Using password: YES)

I m using MySQL 4.0 wiht Exim4.4

Thanks
Sam