[Exim] smtp relay

hi
we are having problem with smtp relay allow for users who have service with
us.we have dial up users as well as hosted domain names with us. we have all
these hosted domain names in a mysql table. and in exim we want to allow
relaying for these domain names thru lookup in mysql.. even if the user is
using other ISP for accessing internet.

what we want is:

If domain is in mysql table then relay ( i.e emails which are created on
these domain names should be able to use our smtp to send email on any host
on the internet, even when the user is accessing internet thru another ISP )
If our dial up IP address and not in table still relay

we have made following changes in config but it seems to be not giving me
expected output.

#relay_domains = mysql;SELECT LOCAL FROM LOCALDOMAINS WHERE LOCAL LIKE
SUBSTRING_INDEX('$key', '.',-2);

#relay_domains = mysql;select LOCAL from LOCALDOMAINS where LOCAL = '$key';

host_accept_relay = 203.73.133.0/19

both of the above mysql queries in relay_domains are not helping me out.

thx
madan