[Exim] relay question

Hi guys,

Can I prevent spamers from using my mailserver with this configuration.
What I want is that only those users in my MySQL database should be able
to use my mailserver for outside relay. I also want my users to use this
mail server from remote location. Can someone please have a look at this
and comment.

......
LOCAL_DOMAINS = localhost:domain.com:computer1:computer2:computer3
local_domains = LOCAL_DOMAINS:mysql;MYSQL_LOCAL_DOMAINS
LOCALUSER_DOMAINS = localhost

host_accept_relay = localhost : 192.168.1.0/24
#host_auth_accept_relay = LOCAL_DOMAINS:mysql;MYSQL_LOCAL_DOMAINS

relay_domains = LOCAL_DOMAINS:mysql;MYSQL_LOCAL_DOMAINS
sender_address_relay = mysql;MYSQL_LOCAL_DOMAINS
sender_address_relay_hosts = mysql;MYSQL_LOCAL_DOMAINS
#relay_match_host_or_sender = true
forbid_domain_literals
local_domains_include_host_literals
never_users = root
receiver_verify
sender_verify
smtp_accept_queue_per_connection = 80
ignore_errmsg_errors_after = 2d
timeout_frozen_after = 7d
..........

Thank you in advance